The board consensus was that Cohn wasn’t well rounded enough to lead the firm. “We’d talk about how we’d ‘crossed the Rubicon’ and he wouldn’t know what we were talking about,” says a former Goldman board member. “But he was unusually bright, knew markets, had huge character, and was straightforward. If you think I’m blunt, he’s right from the brain to the mouth.”

But the man who had made any number of successful bets as a Goldman trader had miscalculated. That quickly proved to be an untenable situation for both Cohn and Blankfein.

A source close to the situation describes what happened at Goldman differently. “The honest-to-goodness story is: did Gary have lunch with Bayo [Adebayo Ogunlesi], Goldman’s lead director, once or twice? Absolutely. Did he ever make a power play to become C.E.O.? He absolutely did not. He met with Bayo and said, ‘Look, is the board comfortable with Lloyd staying on?’ Bayo said, ‘Yeah.’ Gary said, ‘Well, look, that’s great. I know where I am. I’m not in any hurry and I’m not threatening, but we should all be on the same page that I’ve been president and chief operating officer for 10 years.’ Gary gets a lot of phone calls for opportunities. He told Bayo he was going to start listening when his phone rang.”

The timing was perfect for Jared Kushner, Trump’s son-in-law, to pounce. He approached Cohn, supposedly at the suggestion of mutual friends. “Jared Kushner has always been a little starstruck with Goldman Sachs people,” says a former Goldman partner who knows him well. “He’s always liked that sort of promotional edginess that Goldman Sachs has had, and he’s always liked the reputation that Goldman Sachs has the best people, quote unquote, the smartest, savviest people. The idea, by the way, that Jared was suddenly in a position where he actually had the power to call on and hire and lure a number of people like that to the bench side, if you will, was a very, very intoxicating, enticing, and really kind of exciting thing to him,” the former partner continues. “This was an incredibly sort of convenient and opportune kind of thing that came along for Gary because—whether he was going to Washington or not—Gary was out.”

Cohn was the quintessential Goldman executive, with a well-known backstory: a middle-class striver from the heartland who came to the firm and succeeded wildly. From a suburb of Cleveland, the dyslexic grandson of Jewish immigrants, he was pressured by his father to get a job he didn’t want, in the home-products division of U.S. Steel.

On a business trip to New York he visited the comex—the Commodity Exchange Inc., as it used to be known—in Lower Manhattan and eventually talked his way into a job trading options. In 1990 he joined the J. Aron division of Goldman, rising through the ranks, along with his mentor, Blankfein. When C.E.O. Hank Paulson became Treasury secretary, in 2006, Blankfein succeeded him, choosing Cohn to be his deputy.

“I think people respected Gary completely,” says Robert Steel, a former Goldman partner, Treasury official, and New York City deputy mayor who is now the C.E.O. of Perella Weinberg, the boutique investment bank. “I don’t think there’s any issue of him being a jerk or a bad guy or anything like that. He’s very generous. He’s raised a lot of money for N.Y.U. hospital. He has nice kids, one wife. He’s not obnoxious. He looks you in the eye. I’ve never heard him say a single thing derogatory about anybody . . . . He’s never read a five-page memo in his life, but when he asks you to describe something to him he pays incredible attention and remembers every word.”

“I think Mnuchin’s homework is being checked by Gary Cohn,” says a former Goldman partner.

Adds John F. W. Rogers, Goldman’s longtime consigliere, “If you went and talked to most of the bankers at the firm, they would say Gary was a guy who’d go anywhere, anytime, if we asked him to. He was always engaging, and he always brought an interesting market perspective to the dialogue of the problem of the client. He also was an exceptional listener and would look for those common points of moving the conversation forward.”