You could try to spin any conspiracy theory you want, but the simplest explanation in this case is that most people, once familiar with Trump through a close working relationship, see him in a very specific way - as an impulsive child. So Wolff didn't have to "inexplicably found people to tell him", he simply had to interview staff in Trump's administration.
So what do you think is more likely, a fever swamp conspiracy your echo chamber cooked up, or that Wolff simply encountered a consensus among the people he interviewed? I know you will go with a conspiracy theory, but keep in mind that in the White House getting something done without multiple witnesses is outright impossible. This isn't House of Cards IRL with its back stairway.