Now, as Mr. Cohen prepares to head to prison in two weeks, dozens of previously unreported emails, text messages and other confidential documents reviewed by The New York Times suggest that his falling out with Mr. Trump may have been avoidable.

Missed cues, clashing egos, veiled threats and unaddressed money worries all contributed to Mr. Cohen’s halting decision to turn on a man he had long idolized and even once vowed to take a bullet for, according to the documents and interviews with people close to the events. Some of the documents have been turned over to the prosecutors in Manhattan, and a small number were mentioned in the special counsel’s report released on Thursday, which dealt extensively with Mr. Cohen and referred to him more than 800 times.

Mr. Cohen held out hope for a different outcome until the very end, when he pleaded guilty and confessed to paying the illegal hush money to avert a potential sex scandal during the presidential campaign. Just hours earlier, wracked with indecision, he was still seeking guidance, looking, as one informal adviser put it, “for another way out.”