Because almost every former right-winger flocked to fascism out of desperation when BLM started burning entire towns to the ground. There were already major problems before then but that was the tipping point. I know for a fact they didn't want to initially, it contradicted everything they believed in, but it was a scary time and the fascists were the only ones who offered them a solution. And it already had streisand appeal from the media branding it as the opposite of progressivism (to cover their own asses, because it's almost the same thing).

Now there's a huge propaganda effort to erase the libertarian roots of the United States and conservatism. It's very successful because not only are they doing it, but their raging SJW opponents and the media are eager to help, because they've been wanting to smear the right as fascists ever since losing their shit.