He does it because it works. His rabid supporters are highly invested in supporting him. They need to keep supporting him or else they have to see themselves as idiots. So they need something, anything to dismiss any bad reports on him. They are extreme sufferers of confirmation bias. He gives them a reason (fake, rigged, woke agenda, etc) and they use it mentally to dismiss the evidence they can't handle. And then their perception of the lack of any 'real' such evidence allows them to keep believing his bs. It's wild really how people are pulled in like this, and yes it is stupidity and lack of education - but we really need to understand it more to figure a way out of this nightmare.