I strongly recommend watching hbomberguy's video about flat earthers, "Flat Earth: A Measured Response"
https://www.youtube.com/watch?v=2gFsOoKAHZg
The short summary is that flat earthers are probably seen as a rejection of established institutions (like capitalism/neoliberalism) that the (correctly) see as a major source of the problems in their life. Unfortunately, lacking the social/political background required to actually understand these problem, they work with what they can understand.
"The government/etc has been consistently lying to us for decades while our jobs were shipped overseas and our quality of life keeps sliding lower and lower. If they are consistent liars, why should I believe anything they've said?"