I can understand once you follow one FB or Twitter post like this you can get sucked into a whole world of half truths, straw men and conspiracy theories.
I've got a FB 'friend' on there, nice chap but obsessed with all this. He thinks he's somehow saving the world.
He posts things every time some young person dies, implying it must be down to the vaccine, without any evidence of what they died from: cancer, suicide, car accident, we don't know. But yes, it happens at the same time people are getting the vaccine, so there must be a causal relationship (without even knowing if these people are vaccinated!).
But I guess if you follow lots of these people and you read enough about the sinister machinations of Bill Gates, then you might get sucked in to start believing all of it.
Also, I think people have somehow been socialised into believing that if you 'feel' something is right, then it must be true, even if all the evidence goes against it. So they can't be argued out of it because you can't argue with someone's feelings.
Finally I think it gives a strong sense of belonging and status. They're all the true believers and everyone else is just delusional sheeple.