there were enough checks on his power that he mostly managed to simply be incompetent and chaotic
There were no real checks. He had way too many Republicans in Congress for there to be. Most of what protects America is gentleman’s agreements that we all assume a normal president wouldn’t defy.
If the leader of the FBI attempts to investigate him again, they could just hire a new one who won’t.
That is literally what happened last time. The house (where Republicans are a majority) wouldn’t pass a bill that makes firing the FBI director illegal so there’s no real difference.
Fillory and Further by Christopher Plover
within
The Magicians by Lev Grossman