I think many of them have tied themselves politically to Trump so much, and that his appeal to them was always that he "said the things people are afraid to say," told them what they wanted to hear about the "nefarious liberal forces trying to destroy America," and "was always winning," that Trump losing to a democrat in no small part because Trump's a boorish, dangerously incompetent asshole is such a jarringly utter rebuke of everything Trump set them up to believe that they jump to it being some grand conspiracy that they have to rebel against to "protect America."
And of course the man they've followed lo these past four years is telling them yes, that's exactly what happened.
It's been the same with the right wing since the civil war. They're all for political violence to get their way, because no matter who they stand against... whether that be a duly elected president, government employees doing their jobs, or even The actual legitimate United States, they believe that they represent the "god-given decree of what is America." It's practically a holy war for these people.