Calling it an understanding is a stretch, it's ignorance. Or, in other words, an intent to avoid an understanding.
Flat Earth represents the reason fearmonger influencers are so wildly successful online. It represents the reason AI is so successful and so persuasive. It represents the reason we here in my home country of the United States of America currently have a fascist president.
Flat Earthers meme themselves, because they fully represent the chosen ignorance of humans in the modern day. They don't want answers, they don't want truth. They want to be correct, and they think they're "winning" by believing something different than what "big space" "wants them to believe," even though in doing so they are accepting blatant factual inaccuracies, so much so that Flat Earthers will happily change their story the moment it's convenient to still be "right" after they were proven otherwise.
I wasn't going to use the term "stupider," but you said it first.
It is stupidity. A lack of critical thinking, an inability and avoidance to learning, a hatred of knowing. What else would you call these things?
Misinformation kills. Ignorance is bliss, but knowledge is power. Sustainability comes from foresight comes from knowledge, and people who are able to accept a complete and utter disregard for knowledge generally end up breaking stuff and making poor choices due to ignorance. They lack important things to sustain themselves, their friends and family, their relationships, their jobs, etc.. And living a life that's a mess of your own making is not, in fact, bliss.
