“Worst possible person” isn’t accurate but “worst person ever in the role” probably is.
It's... hard to imagine someone worse, in this particular case. Possibly someone who was actively malicious (vs just delusionally insane, which seems to be the case here)?
Within some degree of reason I think it still holds. Yes, if you actively appointed a doomsday cult leader who wants to exterminate the human race, then that would be worse, but that kind of feels like a contrived example.
Within the scope of "people who would realistically actually be appointed", he is the absolute worst case scenario.