They're frightened of everything the other commenter mentioned, but they forgot something: they're frightened that, if "their team" loses power, they will get treated the way they've been treating "the other team" for ages. The grifters know they're lying when they spew their shit, but their followers believe it because it's what they've already done, just in reverse.
"Liberals want to destroy Christianity" is believable because xians have tried their damnedest for nearly 2 thousand years to destroy other religions. "The transgenders want to force all children to change gender" is believable because they've spent decades forcing children into their view of gender, and killing, torturing, or raping them if they don't conform. "Gays want to outlaw heterosexual marriage" is believable because they outlawed gay marriage for ages. "Minorities want to force white people into labor camps" is believable because slavery.
They believe that everyone thinks exactly like them, and they can't fathom that some people want everyone to be happy. They think we're lying when we say that, putting on a front to lull them into a false sense of security just so we can pull the rug out from under them. Because it's what they would do, given the opportunity. And they're terrified of it being turned around on them.
Edit for clarity - and those other things, the vaccines, the healthcare, etc etc, may seem unrelated, but it all comes down to making sure "the other team" doesn't get any "wins". Because if "the other team" wins, that's one step closer to their team losing, and one step closer to "the other team" being able to enact all those horrible policies against them instead of in their favor.