Wells Fargo is taking back another $75 million from two top executives, including the former CEO, blaming them for playing central roles in the bank's fake account fiasco.

The actions announced on Monday were the result of a massive, six-month investigation by Wells Fargo's independent directors into the culture that led to the creation of as many as 2 million fake accounts and firing of 5,300 employees.

Wells Fargo's (WFC) board on Friday took back an additional $28 million from John Stumpf because the longtime CEO was "too slow to investigate or critically challenge" the bank's sales tactics, the 110-page report said.

It also clawed back $47 million from Carrie Tolstedt, the former head of Wells' community banks. Tolstedt and other bank leaders were "unwilling to change the sales model or recognize it as the root cause of the problem," the board found. Directors said Tolstedt and other execs "resisted and impeded scrutiny or oversight" and even "minimized the scale and nature of problems."

Related: 5,300 Wells Fargo employees fired over 2 million phony accounts

Together with previous actions from last fall, Wells Fargo senior executives are returning $180 million in pay. The board report said this is the largest clawback in financial-services history.

Here are some of the major takeaways from the investigation:

'Mass terminations' took place since at least 2002: The nation was shocked that Wells Fargo fired 5,300 employees between 2011 and 2016 for sales abuse. But, actually such mass firings were quite common going as far back as "at least" 2002. The report said "mass terminations" "continued sporadically over the next 10 years." In one instance, an "entire branch" in Colorado was caught breaking the rules by creating unauthorized debit cards. But only "several" employees and managers were fired even though rules required everyone involved be fired.

Early warnings fell on deaf ears: As early as 2004 an internal Wells Fargo investigation titled "gaming" warned that bankers felt they couldn't "make sales goals without gaming the system." That report, sent to Wells Fargo's chief auditor, HR personnel and others, described an "incentive to cheat" that was "based on the fear of losing their jobs" if they didn't make their targets.

'Optimistic' Stumpf was in denial: The board investigation was pretty damning of its assessment of Stumpf, finding that his commitment to the bank's sales culture led him to "minimize problems" despite "growing indications that the situation was worsening." Stumpf's long history with Tolstedt "influenced his judgment" and even led him to ignore doubts about her from directors. In fact, at one point Stumpf even praised Tolstedt to the board, calling her the "best banker in America."

Related: Top Federal Wells Fargo inspector removed

Still, it seemed that Wells Fargo's top management either didn't recognize the enormity of the issue, or made few efforts to address this alarming problem, that was mushrooming fast.

The board said it wasn't until 2011 when a recurrence of events led Wells Fargo employment lawyers to recognize the sales pressure as a "root cause" of the abuse. That year, 13 fired Wells Fargo bankers and tellers at a California branch "charged management with being aware of, encouraging and benefiting from their conduct" and wrote a letter to Stumpf, the report said. In May 2011, Wells Fargo convened a task force aimed at addressing the sales issues to discuss the mass firings and "reputational risk" of the sales goals.

Related: Wells Fargo's whistleblower problem worsens

As part of the latest investigation, Shearman & Sterling lawyers hired by Wells Fargo's board conducted 100 interviews of current and former managers, employees, directors and others and searched through 35 million documents. The lawyers also combed through hundreds of interviews of lower-level employees that were conducted by Wells Fargo.

Wells Fargo's broken culture was first publicly revealed last September, when it reached a $185 million settlement with the government. The news set off a firestorm of criticism and led to Congressional hearings, more than a dozen investigations and lawsuits, the sudden retirement of Stumpf, and forced Wells Fargo to eliminate unrealistic sales goals that promoted cheating.

Related: I called the Wells Fargo ethics line and was fired

Stumpf told Congress last September that he is "fully accountable for all unethical sales practices" and acknowledged he should have done "more sooner" to address this.

During the board investigation, Stumpf was "totally cooperative," though he didn't express "regret" of his actions, according to Stuart Baskin, the Shearman & Sterling partner who led the probe.

Tolstedt did not cooperate with the investigation on the advice of her lawyers, Wells Fargo's board said during a conference call with reporters.

The report hit Tolstedt particularly hard, saying she "resisted change" to the sales model "even when confronted with evidence" it led to improper sales tactics. "Instead, she reinforced the high-pressure sales culture" and was "scared to death" to abandon controversial programs that led to bad sales practices, the board said.

The investigation said Tolstedt "hindered" investigations and kept from the board how many people were fired for sales violations. Incredibly, the board said wasn't aware of the 5,300 firings, and found out at the same time as the public when it was mentioned in the September 2016 settlement.

"We strongly disagree with the report and its attempt to lay blame with Ms. Tolstedt. A full and fair examination of the facts will produce a different conclusion," Enu Mainigi, Williams & Connolly lawyer representing Tolstedt, said in a statement.

Former Wells Fargo employees have described an atmosphere of fear, where they were scared of speaking up about illegal activity. Almost half a dozen Wells Fargo workers told CNNMoney last year that they were fired after calling the bank's confidential ethics hotline. More recently, the federal government ordered Wells Fargo to rehire one fired whistleblower and warned it may force the bank to welcome back another.

Related: Elizabeth Warren's epic takedown of Wells Fargo CEO

However, the board report released on Monday said that after a "limited review" Shearman & Sterling "has not identified a pattern of retaliation" against bank employees who complained about sales pressure or practices.

Sloan, who replaced Stumpf as CEO, appears to have emerged from the investigation largely unscathed.

Wells Fargo Chairman Stephen Sanger said the board does not "anticipate any further employment or compensation actions" stemming from this investigation.

Sanger said that the investigation "found that Tim had very little contact with sales issues" because he mostly worked in a different part of the bank. While Sloan didn't come up through the community bank, he did serve as a senior executive as chief financial officer and chief administrative officer.

Still, Sanger said the board has "total confidence in Tim" and is "very, very encouraged" by the actions he took once he became CEO, including replacing Tolstedt.

The scandal has put pressure on Wells Fargo's board, too. Last week Institutional Shareholder Services, a shareholder watchdog group, recommended that Wells Fargo investors vote against the directors due to lax oversight.

Asked why he shouldn't step down as chairman, Sanger acknowledged that the Wells Fargo board could have "pushed more forcefully" to remove Tolstedt. However, he said the report found the board "took the appropriate actions" once it became aware of the problem.

In a separate statement, Wells Fargo CEO Tim Sloan called the board's findings a "critical part of our journey to rebuild trust" and acknowledged management "took too long to understand the seriousness and scope of the problem."

Sloan promised that the tactics and pressure that hurt employees, customers and the Wells Fargo reputation "will never be allowed to occur again."

Senator Elizabeth Warren, one of Wells Fargo's toughest critics, said on Twitter that the clawbacks are a "good step," but "no substitute for a thorough" government investigation.

Wells Fargo still faces around a dozen investigations and lawsuits, including probes from the SEC and Department of Justice.

--To reach the author of this article email Matt.Egan@cnn.com