In late 2011, as the bank debated whether to resume lending to Mr. Trump after his 2008 defaults, a senior executive asked Josef Ackermann, who was in his last months as chief executive, about the potential loans. Mr. Ackermann gave a thumbs up, according to people familiar with the process. (Mr. Ackermann said in an interview that he didn’t recall being involved.)

His successor, Anshu Jain, was briefed on the Trump relationship early in his tenure. In February 2013, Mr. Jain accompanied Rosemary T. Vrablic — Mr. Trump’s personal banker at Deutsche Bank — to Trump Tower in Manhattan, according to two former executives. Over lunch, Mr. Jain remarked to Mr. Trump that he was surprised by his relatively low levels of debt. Ms. Vrablic told her colleagues that Mr. Jain had sounded upbeat about Mr. Trump’s finances.

Deutsche Bank’s board found problems with its Trump lending.

In 2016, the board of directors commissioned a report into how the bank had become so enmeshed with Mr. Trump.

The report, prepared by the board’s integrity committee, concluded that Deutsche’s private-banking division, which catered to very rich individuals, was so determined to win business from big-name clients that its executives had looked past Mr. Trump’s history of stiffing his lenders and for engaging in demagogy, according to a person who read the report.

The review also found that Deutsche Bank had produced a number of “exposure reports” that flagged the growing business with Mr. Trump, but that they had not been adequately reviewed by senior executives.

Board members found that the Trump relationship was a symptom of a broader problem with the bank’s siloed management structure and a culture of getting deals done at all costs.