The Newt and the Tea Party started the slide, normalizing hatred and bombast and FU-politics, and MAGA perfected it.
Whether you love it, hate it, or are indifferent, what you are dealing with now are not really Republicans. They are MAGA-folks. They should really rename themselves the Solipism Party. Nothing matters but the current state of your own head.
And yes, I know parties change and evolve with the times, but I would argue this time is very different.