Because despite all their saber rattling, the MO for US Republicans is to do things like ban books, sue teachers for teaching history, shun journalists, etc.
The Republican share in the last 6 Presidential elections is 47%, 46%, 47%, 46%, 51%, 48%, the outlier being Bush's reelection in 2004. There's nothing special about Trump, electorally speaking. Republicans vote Republican.
"at 44.95%, Trump had the lowest percentage of the popular primary vote for a major party nominee since the 1988 Democratic Party presidential primaries."
"A total of 17 major candidates entered the race. Prior to the 2020 Democratic Party presidential primaries, this was the largest presidential primary field for any political party in American history."
https://en.wikipedia.org/wiki/2016_Republican_Party_presiden...
Trump had a number of advantages:
1) He was already super famous.
2) He was an experienced TV actor and entertainer.
3) He was rich.
4) He was a non-politician, which voters like, because they hate politicians.
5) He dominated every news cycle by continually saying wildly controversial things. The news media showered him with coverage over every other candidate.
Some in that party jumped on the feminist train and today nearly supports the opposite of what it once stood for. They complained about too many men and sexism in the party. Duh... Today they are yesterdays news but the party never really recovered and also left many politically homeless. Some of those vote for more radical parties.