Also in some cases it gives them a built-in sense of community and belonging, something they haven’t experienced. The documentary Behind the Curve does a good job of pitying flat earthers rather than just ridiculing them. (Though they are absolutely subject to ridicule.)

I think it's also about cult mindsets. If a scientist says the earth is billions of years old that also means there's no heaven and the alienated existence under capitalism is all you get. There's a phrase I heard from religious-types: "would you rather this be the closest you get to heaven or hell?" They really see earth as hell and are only here to recruit and die.