I wondered the same thing and then stumbled over “Behind the Curve” on Netflix. It was an eye-opener. You’ll learn where it came from and more importantly, how to handle people with these beliefs. It changed the way I will approach the topic for sure. The earth is round! Don’t misunderstand me, but the psychology that drives flatearthers is fascinating and we can help them find the right “path”.
It’s a great watch! Highly recommended :)