Because it doesn't matter.
What has happened in the States isn't about logic, it's about identity.
MAGA don''t give a shit about the likes of FogBlueInSanFran, what's important is what hurts the likes of FogBlueInSanFran, that's what's important, it's more than that it's great! Deep, deep, really deep they despise what he stands for, they're taking their country back from the likes of him.
Trump is a monumental arsehole, his rambling incoherent speeches, his appalling performance as President, and yes in the end the rubber hits the road and he's found out, nevertheless he keeps rising from the dead and the only way to understand why, is to realise that despite his obvious shortcomings, his unsuitability to lead the most powerful country in the world. he knows how to tap in to that visceral hatred.
Huge sections of American society simply despise each other, Trump knows that, that's why he wins.