Mostly it is because of gerrymandered districts. If you come from a safe district you can be as crazy as you want to be and you don't have to compromise.
Gerrymandering is a "both sides" thing for sure but I will in no way excuse the Republican need to systematically dismantle our democracy by undermining institutions and fomenting divisive culture war wedge issues to the point of violence. Democracy works best when everyone is involved so the Rs can choke on a bag of dicks when they start gargling about voter suppression under the guise of "election integrity."