Trump’s biggest mistake was trusting people in his inner circle whom he should have never trusted. He has so many knives in his back that he ought to be called Caesar.
Kushner, Pence, Barr, Omarosa and on and on and on. Every one of them gave him advice and counsel that was either self-serving (Kushner) or running interference for the Deep State (Pence, Barr, etc.)
I do not question his patriotism nor his heart. His judgment in selecting his inner-circle, on the other hand...
Here is the trouble Trump had
1. He doesn’t have anyone who he can trust outside his family. Pretty common among high level executives.
2. The quality people who know the job are opposed to everything he stand for. So you won’t get a career politician to work for Trump. It is a career ending move.
3. Any staffer or such that works for Trump finds themselves locked out of a future. That attracts either the very young, or the ready to retire.
4. Trump is Trump. He is a megalomanic at best. Not a barrier to office, but Trump is a showman. In the open. No filter. Wild swings. For a system with people in it for over 50 years, that is impossible to deal with.