A basic education (assuming grade school level) would only inform you that the world isn't flat. It wouldn't go so far as to rigorously prove the idea. In fact,

A basic education (assuming grade school level) would only inform you that the world isn't flat. It wouldn't go so far as to rigorously prove the idea. In fact, I honestly couldn't prove to you that the world isn't flat myself off-hand. My "knowledge" of the unflat world is really just trust in prior mathematicians and scientists who I believe have proven the idea. I think this continuum between knowledge and belief is where these crackpot ideas are coming from. The average person doesn't know how the things they depend on actually work on a deeper level (e.g. the internet, cars, indoor plumbing, seasonal weather, the stock market). And upon researching the inner workings of these day-to-day mysteries, people realize that the mechanisms aren't 100% clear or they don't fully understand them. I'd wager this is the diverging point: most people give up on learning the mechanisms and accept that they work on belief while a small portion of people come up with alternative hypotheses and/or reject the mechanisms. A recent episode of This American Life discusses this (https://www.thisamericanlife.org/radio-archives/episode/630/things-i-mean-to-know https://www.thisamericanlife.org/radio-archives/episode/630/...).