Because trump is much, much more popular among republican voters than they are. If they criticize him, they will be primaried and lose their jobs. So instead they play along or hide and refuse to comment.
THANK YOU! Yes. Many Republicans are quite intelligent (even Ted Cruz is not the bumbling idiot he appears to be). The Republicans in Congress know Trump is not a fit leader. They know that he is corrupt and they know how much he lies. Most Republicans are smarter than Trump! But they are afraid of the voters. And Trump CONTROLS the bulk of republican voters.
Trump, much like a cult leader, commands the emotional loyalty of millions who have felt angry and invisible for years. Without a formalized system of logic (definitely not saying they are inherently stupid -- they're not), the Trump followers seem incapable of overriding his direct appeal to their emotional limbic system. I'm no exception. I dislike Trump to the point of addiction.
I mean, I took one look, and knew instantly that he was nothing more than a con-man with an incredibly fragile ego. Trump supporters see something different I think.
One of the many problems with democrats, is that they SELDOM EVER know how to appeal to people's emotions (the real reason we do everything). They come across boring, which is probably how it should be. We should be governed by logic, not our base emotions. But for the average person, emotion in politics looks like passion, inspiration and very often, the truth. "It makes me feel good, therefore it must be true."
As for the Republican lawmakers, I believe they would MOST CERTAINLY speak out against Trump, if 73 million people hadn't voted for him. Most Republicans (office holders) are not so loyal to Trump, as they are loyal to his devoted VOTERS! I'm not saying this is okay, because IT ISN'T!
In fact, to this I say, COUNTRY OVER PARTY people! COUNTRY OVER PARTY!
(independent)