> If the GOP has such disdain for Trump, then why do traditional conservatives in Congress continue to support him?

Probably two reasons:

1) They fear his base, which can mount primary challenges to unseat them when they're open with their distain (see: Flake, Jeff).

2) Trump has been useful in allowing them to pursue much of their traditional agenda: tax cuts, deregulation, court picks, etc.

Because they are more closely aligned with the populist wing of the Republican party than the neo-conservative/elitist/globalist wing of the Republican party. The elitist wing has been the dominant force in the Republican party for decades at least.