Those overflowing crowds of Trump-cultists at rallies has petrified the republicrat politicians.
No one wishes to be primaried and removed. It has to be bigger shame than losing to opposition party.

Conservatism is about preserving the "traditional hierarchical structure of Western societies" which has been present since the time of monarchical government. The monarchy was replaced by the Capitalist. The wealthy White business person is the replacement for the nobility. Republicans can scream all they want about "freedom", "family values", and all that other bullshit they care nothing about; the reality is that they want to preserve the power structure as it has been historically but there aren't enough wealthy White people to "vote" it into reality so they have always had to lie and cheat.

Today's conservatives threw their lot in with Trump because the racists and Christian dominionists who the Republicans would use then discard, were tired of it. There was no enthusiasm for a Jeb Bush, Marco Rubio, or even Ted Cruz presidency. Trump did away with the dog whistles and coded language and used clearly racist, sexist, and Christian dominionist language to bring them along once more.

They are stuck and have to go all in because they do not have the numbers to sustain their usual bullshit.