Using the initials for North Korea’s formal name, the Democratic People’s Republic of Korea, Mr. Carafano added: “If D.P.R.K. doesn’t come through, then his supporters will give him chips for trying, we are no worse off and D.P.R.K. is just as isolated, no matter how many selfies Kim has with Trump.”

The selfie with Mr. Kim was Mr. Trump’s most celebrated and criticized act during his trip, the one that put on display his flair for improvisation and spectacle. No other president would have posted a message on Twitter inviting North Korea’s dictator to meet him at the Demilitarized Zone barely 24 hours later and then step over the line to become the first sitting president to enter North Korea.

In another administration, such a move might have been deliberated for weeks, put through an interagency process and approved only as part of a comprehensive approach to pressuring North Korea into giving up its nuclear program — a reward for progress. Mr. Trump himself had previously been talked out of just such a move by cautious advisers. But this time he could not resist the idea of a showy “first,” whether it fit a long-term strategy or not.

In creating his preferred version of the story, Mr. Trump said he just came up with the idea when he woke up in Osaka on Saturday morning and spontaneously posted the message on Twitter. It was true that he caught his aides off guard, forcing them to scramble to see if a tweet could be turned into reality.

But it was not true that he just thought of it Saturday morning. He had talked about it at least five days earlier with journalists for The Hill news organization, which was then asked by the White House not to reveal that out of security concerns.

As with so many things, that reality did not fit neatly into the story line Mr. Trump was fashioning, so it was disregarded. The other part of his chronicle was how he was cleaning up the “fiery mess” he said was left by Mr. Obama.

He claimed that Mr. Obama wanted to meet with Mr. Kim only to be rebuffed and that had the last president stayed in office, he would have gone to war with North Korea — a pretty fanciful revision of history, according to advisers to the former president, but one that suited the heroic epic Mr. Trump was writing for himself.