Donald Trump denied knowing at the time the January 6 attack on the US Capitol started that a mob of his supporters – whom he privately called “fucking crazy” – were rioting, the author of a forthcoming book on his chaotic presidency writes in what may stand as one of the most surprising, non-believable postscripts of his tenure in the Oval Office.

“I didn’t usually have the television on. I’d have it on if there was something. I then later turned it on and I saw what was happening,” Trump told New York Times reporter Maggie Haberman for her forthcoming account Confidence Man: The Making of Donald Trump and the Breaking of America.

“I had heard that afterward and actually on the late side. I was having meetings. I was also with [then-chief of staff] Mark Meadows and others. I was not watching television.”

Trump’s comments on what Haberman describes as one of the persistent mysteries of January 6 – what he was doing during the deadly Capitol attack – comes despite congressional testimony that he was indeed watching events that day in early 2021 when his supporters tried desperately to prevent the certification of his defeat to Joe Biden in the presidential race weeks beforehand.

In an extract published in the Atlantic, Haberman writes that she was given three post-presidential opportunities to speak with Trump and found that “his impulse to try to sell his preferred version of himself was undeterred by the stain that January 6 left on his legacy and on the democratic foundations of the country – if anything, it grew stronger”.

At Mar-a-Lago, Trump’s “Winter White House”, the former president appeared “diminished”, she writes.

Haberman continued: “After the headiness of being at the center of the world’s gaze, his time after the White House made him seem shrunken.

“He often played golf and then went to his newly built office at the club for meetings with whoever traveled down to seek his approval.

“He would watch television before going to dinner, where club members would sometimes applaud him, and then it would start all over again the next day, so removed from the daily rhythms of the broader world that he was oblivious to holidays on the calendar and staff had to remind him.”

Within the book’s pages, Haberman reports that Trump dissed his supporters to aides ( “They’re fucking crazy”) ; that she found it “difficult to discern, though, whether Trump actually believed what he was saying about the election”; that while president he considered he was doing two jobs: “running the country and survival”.

Asked about a second run for the presidency, Haberman writes, Trump “was more comfortable looking backward than forward. When I told Trump I wanted to talk about 2024, he asked, quizzically, ‘2024?’”

In typical Trump style, he insulted allies that he felt had turned against him, saying of Senate minority leader Mitch McConnell that “the Old Crow’s a piece of shit”.

The former president also ruminated that he would not be facing civil indictment for fraud in New York under ex-state attorney general Robert Morgenthau, and he claimed that he had not taken important documents from the White House at the end of his term.

“Nothing of great urgency, no,” Trump told Haberman, except letters from North Korean leader Kim Jong-un with whom, he hinted, he was still in touch.

Asked if he would do it over again, Trump said that he gets asked that question more than any other. “The answer is, yeah, I think so,” he said, according to Haberman. “Because here’s the way I look at it. I have so many rich friends and nobody knows who they are.”

Ultimately, Haberman concludes, Trump “works things out in real time in front of all of us. Along the way, he reoriented an entire country to react to his moods and emotions.”

To understand him at all, she writes, one would first have to understand the New York from which Trump emerged – “its own morass of corruption and dysfunction”.

“I spent the four years of his presidency getting asked by people to decipher why he was doing what he was doing, but the truth is, ultimately, almost no one really knows him,” Haberman writes. “Some know him better than others, but he is often simply, purely opaque, permitting people to read meaning and depth into every action, no matter how empty they might be.”