Most of the Flat Earther's I've met are smarter. The others just blindly accept what they're taught in school, university, etc. Flat Earthers take this, apply it to real life, and find the ball-Earth stuff doesn't actually work.
The Flat Earthers I know have often been top of their fields. I knew a man who served many years in the military working with torpedoes. Most of the people who realise or learn the Earth is flat won't just go around admitting it to everyone. Most people are so indoctrinated with lies, they will mistake a genius speaking the truth for a madman if the evidence is not introduced more slowly and carefully.