Don’t get me wrong; I’ve personally experienced the “life collapsed, everything was a lie, rebuild from here” thing. But where these people fall flat (no pun intended) on their faces is that in not having that information (as you described), they choose instead to not even bother trying to get it. They’re totally fine with willful ignorance because they’re too afraid of being lied to again to ever actually stand up for anything, least of all themselves.

And so yes, anyone who can’t do basic elementary school trigonometry or geometry is perfectly capable of thinking the Earth is flat. They just also need to be kept from voting and from leaving the insane asylum.