Short term will be bad. Maybe BAD bad. But the coalition they have, between corporate interests, Nazis, and feudalists has no way of holding together. All three are pulling in very different directions and if there was someone else capable of riding that dragon they would have been found by now.
Basically, no one is willing to die for JD Vance.
If there was someone better at it, they would be president. I guess the worst fear is someone close enough to his personality to keep it together but also be somewhat competent
You can't APPEAR to be competent and still be Trump. His entire magic trick is that everyone who spends more than a few minutes with him are convinced he's an easy mark they can manipulate. So far, they've all been wrong.