The Room Where It Happened: A White House Memoir by John Bolton:
In an October 2019 interview, in the midst of the Ukraine impeachment crisis, Kelly said he had told Trump, “Whatever you do—and we were still in the process of trying to find someone to take my place—I said whatever you do, don’t hire a ‘yes man,’ someone who won’t tell you the truth—don’t do that. Because if you do, I believe you will be impeached.” Trump flatly denied Kelly had made such a statement: “John Kelly never said that, he never said anything like that. If he would have said that I would have thrown him out of the office. He just wants to come back into the action like everybody else does.” And Stephanie Grisham, previously one of the First Lady’s Furies, now White House press secretary, pronounced ex cathedra, “I worked with John Kelly, and he was totally unequipped to handle the genius of our great President.” These quotes speak volumes about the people who uttered them.
With Kelly’s departure and Mulvaney’s appointment, all effective efforts at managing the Executive Office of the President ceased. Both domestic policy strategy and political strategy, never strong suits, all but disappeared; personnel decisions deteriorated further, and the general chaos spread. The crisis over Ukraine followed. There was a lot of evidence that Kelly’s hypothesis was entirely correct.