I've actually spoken to a few Flat Earthers and without exception they have all been completely ignorant of even the most basic understanding of pretty much anything at all, they have all been emotionally damaged - very angry people underneath a thin veneer of normality - and are almost always found among life's misfits, failures, and under-achievers. Believing that only they know "the truth" appears to give them a fragile illusion of competence and importance that they lack in reality. So conspiracy theories are basically very poor-quality psychological compensation mechanisms. In older times these people would have been Witchfinders, prying village gossips, and extremely low-level government bureaucrats.