Same answer it’s been for my whole lifetime: a small number of extremely wealthy individuals pumping a constant stream of money into conservative media with the express purpose of changing public opinion.
People who’ve been listening to this stuff their entire lives don’t live in the real world. They legitimately don’t believe in reality, and after a certain point I’m not sure it’s possible to bring them back. Much like climate change, this kind of thing should’ve been stopped at the source decades ago, and it might just be too late now.
With the now-totally-legal-thanks-to-SCOTUS voter purging, theft and destruction of ballots, aggressive voter suppression tactics, and polling that indicates an electoral college but not population vote win for Trump, they might not have to ‘Stop the Steal’ at all. They’ve “legally” pre-stolen it themselves.
Instead of being concerned what the Republicans might do if they lose, it might be worth wondering if everybody else should really take it lying down like they did the 2000 election.