For months, the text messages came. Some were flirtatious, asking her to meet him late at night. Sometimes, the texts were sexually explicit.

The messages were directed at Laura Munoz, an executive assistant at the online lending start-up Social Finance. The texts were from her boss, Mike Cagney, the company’s chief executive, according to five people who spoke with Ms. Munoz or saw the messages. Given Mr. Cagney’s stature at Social Finance, known as SoFi, Ms. Munoz was at a disadvantage.

That became apparent when SoFi’s board was informed of Mr. Cagney’s communications with Ms. Munoz in late 2012. The board said it found no evidence of a sexual relationship. Ms. Munoz was then paid about $75,000 to leave the company, according to three people familiar with the proceedings who spoke on the condition of anonymity because they were not authorized to talk publicly. Ivo Labar, a lawyer representing Ms. Munoz, said matters were resolved between his client and SoFi.

Around the same time, SoFi’s board and executives also heard complaints from investors that Mr. Cagney had made misstatements to them over the start-up’s student loan products, according to emails between investors, executives and the board that were obtained by The New York Times. Directors stood by Mr. Cagney in that instance, too.

The board’s support allowed Mr. Cagney to build SoFi into a fast-growing start-up that is trying to take on the big banks by offering lending, insurance and asset management online. The company has been valued at more than $4 billion.

But within SoFi, Mr. Cagney, a married father of two, continued to raise questions among employees with his behavior. He was seen holding hands and having intimate conversations with another young female employee, according to six employees who saw the two together. At late-night, wine-soaked gatherings with colleagues, he bragged about his sexual conquests and the size of his genitalia, said employees who heard the comments.

Mr. Cagney’s actions were echoed in other parts of SoFi. The company’s chief financial officer talked openly about women’s breasts and once offered female employees bonuses for losing weight, according to more than a dozen people who heard his comments. Some employees said on a few instances, they caught colleagues having sex with supervisors at SoFi’s main satellite office in Healdsburg, Calif., which was the subject of a sexual harassment lawsuit filed last month.

Even as other Silicon Valley companies such as ride-hailing giant Uber have been in the spotlight this year for inappropriate treatment of women, Mr. Cagney’s case goes a step further. Although many of the issues at other firms stemmed from the actions of midlevel executives or investors, Mr. Cagney personally faces questions about his role. His conduct was described by more than 30 current and former employees, most of whom asked to remain anonymous for fear of retribution.

The behavior went largely unchecked until Monday, when SoFi’s board acted after weeks of growing scrutiny of the company. The start-up said Mr. Cagney, 46, would leave as chief executive by the end of the year and that he would step down immediately as chairman. In a statement announcing Mr. Cagney’s departure, SoFi did not explain the executive change.

Read more from the New York Times:
Purged Facebook page tied to the Kremlin spread anti-immigrant bile
At Google, employee-led effort finds men are paid more than women
How Jake Paul set the internet ablaze

The company said its business was performing well, and that SoFi was becoming a “major, innovative player in consumer finance.” A SoFi spokesman said the company did not comment on personnel matters and disputed that its business had taken on too much risk. Through the spokesman, Mr. Cagney also said he “vehemently denies” any improprieties at after-hours events with colleagues.

Yet Mr. Cagney’s position had become increasingly delicate after the filing of the sexual harassment suit, which accused him of “empowering other managers to engage in sexual conduct in the workplace.”

His situation was also exacerbated by claims about his approach to SoFi’s business, which uses money from Wall Street investors to fund student loans, personal loans and mortgages. At several points, Mr. Cagney ignored warnings from colleagues that he was being too aggressive with the business, according to more than a dozen employees who were involved in the conversations.

That included a time when Mr. Cagney decided to put customer service representatives in charge of lending determinations, despite them having no experience in the area. Another time, he told investors that SoFi had $90 million in debt financing for a loan product; the company did not in fact have the money, according to the internal emails reviewed by The Times.

SoFi’s board, which includes representatives of Japanese conglomerate SoftBank and the influential hedge fund Third Point Capital, now faces questions about whether it needed more checks and balances on Mr. Cagney.

Companies like SoFi show how boards are incentivized to prioritize cash flow and growth over governance, said David F. Larcker, a professor at Stanford University’s Graduate School of Business who specializes in corporate governance. “The board now has a duty to correct for things that have gone wrong,” he said.

The board said that it found “no allegation or evidence of a romantic or sexual relationship” between Mr. Cagney and Ms. Munoz and referred all other questions to SoFi.

Mr. Cagney, who was born in New Jersey, started his career in finance in 1994 at Wells Fargo, where he climbed the ranks to the trading desk. He later left the giant bank to begin a financial software company, and then his own hedge fund, Cabezon, in 2005. On the side, he attended Stanford’s business school.

In 2011, Mr. Cagney began SoFi with several co-founders. The start-up, established as venture capitalists were getting excited about financial technology, raised nearly $100 million in its first year. In total, SoFi has now taken in $1.9 billion from investors including SoftBank, Discovery Capital and Baseline Ventures.

Even with other co-founders, Mr. Cagney quickly established himself as the company’s center of gravity. SoFi’s offices, with glassed-in conference rooms and cheap Ikea furniture, were set up in San Francisco’s Presidio, the park near the Golden Gate Bridge, because Mr. Cagney’s hedge fund already had its offices there. His home was less than a mile away.

Mr. Cagney exhibited an aggressive attitude at the office that he may have learned as a trader at Wells Fargo. He sometimes shouted obscenities and excoriated employees in front of others when they made mistakes.

Mr. Cagney hired deputies who had similar characteristics. One was Nino Fanlo, a former executive at Goldman Sachs and the private equity firm Kohlberg Kravis Roberts, who became SoFi’s chief financial officer in 2012.

Mr. Fanlo, 57, sometimes kicked trash cans in the office when angry. He also commented on women’s figures, including their breasts; said that women would be happier as homemakers; and once told two female employees he would give them $5,000 if they lost 30 pounds by the end of the year, according to more than a dozen people who heard the comments and witnessed the weight-loss offer.

Mr. Fanlo said it was “patently false” that he did not respect women and that his team at SoFi had many women who received promotions and professional accolades. He also attributed his shouting and kicking of trash cans to frustration about deals and start-up pressures.

“You’re under extraordinary pressures at a company that is growing that fast,” Mr. Fanlo said.

More than two dozen former SoFi employees said they were uncomfortable with Mr. Cagney’s pursuit of women in the office. In 2012, he sent the text messages to Ms. Munoz, the executive assistant, until her colleagues took the issue up with executives and the board, according to the five people who spoke with Ms. Munoz about the matter.

Even as Mr. Cagney was texting Ms. Munoz, he also chased another young female employee. Six employees said they saw Mr. Cagney and the employee holding hands and talking intimately. One day in 2013, when Mr. Cagney was flirting with her at the office in front of colleagues, she grew enraged and left, according to three employees who witnessed the episode. Soon after, she left the company.

Around that time, SoFi’s board asked Mr. Cagney to not engage in inappropriate conduct with employees, according to two people with knowledge of the conversations. The situations were awkward in the office given that Mr. Cagney’s wife, June Ou, began working at SoFi in 2012, rising to become the company’s chief technical officer. Her desk was near Mr. Cagney’s. Ms. Ou did not respond to a request for comment.

SoFi’s business works in the following way: It loans money to students, home buyers and individuals with high credit scores. The company funds those loans with money from hedge funds and banks, who buy the loans through securities or bonds that SoFi creates.

As early as 2012, Mr. Cagney ran into trouble with some of his investors. That year, the company said it had secured $90 million in debt financing for one of its loan products, called Refi A. But some investors who had bought the securities noticed their returns were not in keeping with SoFi’s estimates and voiced concerns to executives and to a board member, according to the emails obtained by The Times.

About 10 SoFi executives met to discuss the situation; it was then that some of them learned Mr. Cagney had not actually secured the $90 million for the loan product, according to people who were at the meeting. Some attendees said they were dismayed at the possibility that they had made material misstatements to investors.

In October 2012, SoFi bought back the Refi A securities from investors for what they had paid, plus the investment return they had anticipated, or gave them the option to put their money into a different product. Mr. Cagney said in an investor letter that the product had been “imperfect,” but did not offer any details about the $90 million. The SoFi spokesman said that “no consumers were harmed in the process.”

In 2015, SoFi began offering mortgages. In meetings with the compliance officer overseeing the program, Mr. Cagney was told that SoFi was not doing enough to document the income of borrowers and was rushing to offer loans more quickly than competitors did, according to a person involved in the mortgage business. A SoFi spokesman said the company complied with all laws.

Mr. Cagney also led a push into personal loans last year. To strengthen that business, he asked customer service representatives to review and approve loans, a job that had previously been done by the company’s underwriters, said two people involved in the loan business. Many employees opposed the change because customer service representatives do not have the experience of approving loans, but the move helped SoFi double the amount of loans it issued in just a few months.

That created another problem: SoFi did not have enough money to fund all the loans it was giving out. Mr. Cagney told employees that because of the funding shortfall, it could take as long as 30 days for some new customers to get the money they borrowed. But the employees who dealt with the customers were told by a supervisor to say that people would still get the money within 72 hours as promised.

“We had to lie to them and tell them that we were a little behind or that the transfer got lost — just something to keep them off our backs,” said Marie Lombard, who worked from 2014 to 2016 at SoFi’s operations center in Healdsburg.

Mr. Cagney eventually took customer service representatives off the underwriting decisions.

A SoFi spokesman said that customer service representatives did not approve loans and that the company’s proprietary software made those decisions. He added that SoFi always communicated timing changes on its loans to borrowers and that delays have never run as high as 30 days.

Mr. Cagney’s risk-taking outside of SoFi also created problems. In January 2015, his hedge fund, Cabezon, suffered big losses on a currency trade. In the aftermath, SoFi’s board agreed to buy Cabezon for $3.25 million and give the hedge fund’s employees jobs at SoFi. That caused resentment at SoFi among some workers.

A SoFi spokesman said the company bought Mr. Cagney’s hedge fund partly because the board was concerned about Mr. Cagney’s ability to focus on both companies.

At the time, SoFi was growing rapidly. Since 2011, when it had five people in a one-room office, the company has grown to 1,200 employees and lent more than $20 billion to about 350,000 customers. Earlier this year, the private equity firm Silver Lake Partners led a new round of fund-raising that gave SoFi another $500 million and valued the company at $4.3 billion.

Mr. Cagney’s co-founders nonetheless left the company one by one, and Mr. Fanlo departed this summer. (Mr. Fanlo said that he left to pursue a new opportunity.)

In 2015, an anonymous email was sent to everyone in the company, complaining in detail about the work environment and nepotism in hiring, according to five employees who received the email. SoFi said that it takes every complaint seriously.

At the start-up’s office in Healdsburg, Yulia Zamora, who worked as an underwriter there from 2015 to 2016, said it often seemed as if there were no rules. She said she was propositioned by a supervisor numerous times.

“It was a frat house,” Ms. Zamora said. “You would find people having sex in their cars and in the parking lot. It was a free-for-all.”‘

SoFi has recently been taking steps to contain the damage. Earlier this month, the company started an investigation into the harassment claims in the Healdsburg satellite office. At the same time, questions over Mr. Cagney’s own behavior also surfaced.

In recent days, Mr. Cagney canceled a trip to Singapore to attend a board meeting at SoFi’s offices in San Francisco on Monday. At the meeting, Mr. Cagney argued for his job — but eventually lost out to board members who viewed him as a liability, according to two people with knowledge of the meeting.

“I want SoFi to focus on helping members, hiring the best people, and growing our company in a way consistent with our values,” Mr. Cagney wrote in a letter announcing his departure. “That can’t happen as well as it should if people are focused on me, which isn’t fair to our members, investors, or you.”