They lost the election for a lot of reasons but party loyalty isn't one of them.
They had no message to run on. They've been the "we're not Trump, vote for us" party for so long they forgot what that stand for, which isn't much.
Plus Trump showed the nation that we actually don't have to put up with all of the insanity coming out of that. Most of it so far away from any form of sanity. The left is very good at creating false accusations to brow beat people into following along.
Trump just steamrolled all over that and America woke up.