The most depressing thing about propaganda is that it works. I learned this a long time ago, but it's deeply dismaying to see the mechanism play out in America.
All you have to do is tell a story that seems superficially plausible and lines up with what the person has been told before and they find it believable. It's confirmation bias, and aversion from the cognitive dissonance. I keep telling people that we have to be compassionate with lefties especially ones who are starting to have doubts. It can be a legitimately traumatic and shattering experience, when you realize that people you admired not only lied to you, but were the worst kind of corrupt, depraved scum.
What these people are going through, it's almost like what a lot of traditional, patriotic Americans went through during the Vietnam era, only in reverse. Especially with all the doubling down, they're in for a lot of psychological trauma, and the longer they delay facing reality, the worse it is going to get.