It’s being driven by Trump’s authoritarian control over the party
The best example of this is the hapless Senate candidate Larry Hogan, who meekly called on the public to respect the jury verdict; Trump’s campaign manager immediately responded publicly that Hogan’s campaign is “over.” If Trump comes into conflict with the criminal justice system it must be the criminal justice system that’s the problem. That is what he requires of his supporters and that’s what they give him.
What are the chances Trump is the One Ring and the GOP just crumbles to dust when he’s finally out of the picture?
(I know, I know. He’s the festering symptom not the root cause. I can dream, though)
Low.
The patronage machine that makes the Republican party tick is still around.
It’s easy to see a period of worsened infighting though. Right now, there is a litmus test that’s basically “support whatever Donald Trump tells you to support,” without any coherent ideological basis. When Trump’s gone, who delivers the message about what to believe? I think there will be a lot of disagreement
As is tradition, the one inheriting such an organization devolved to support fascism, bigotry, exploitation and inequality will be whoever most exudes those qualities from the base. A successor can never have the same schtick though, the generally have to push further to stand out. The very nature of extremism’s slippery slope, what follows will be worse until, as op said, the cleansing fire, purge or Mt doom happens.