A minor quibble.

I think those people were always there, you just couldn't see them. They were hiding under rocks, with the internet their only outlet for their vileness (just look at the Yahoo message boards of old, or even YouTube comment sections). But Trump was "one of them", and he normalized thuggish and racist behavior, and so the thugs and racists came out from under their rocks because they thought their time had come. Their behavior and attitudes were acceptable. MAGA was born. It will take time for them to go back into hiding, but they will always be there.

Note: I am not referring to all Reps. Just the subset of MAGA. Many other Reps are complicit, even if they disapprove, because there is power in MAGA, and they were winning elections for a cycle or two. But it's a tiger that they can't control, and it's destroying them. And now they're (mostly) losing elections with Trump-endorsed candidates underperforming significantly.