IMO you can't say anything coherent about most US-based right wing conspiracy theories without understanding how seriously the diehards in these movements believe in The Devil
the obvious question, "who benefits from maintaining this elaborate lie," does not stop people like Flat Earthers because many of them are young earth creationists who believe in powerful spiritual forces whose only goals are
1. convincing people that Christianity isn't true
2. the proliferation of largely symbolic Evil, which they enjoy tricking you into supporting
"tricking" people into believing the earth is round is enough of a goal for The Devil to go to all that trouble. if people don't believe in God's perfect little flat earth then they're also free to believe in things like evolution and the big bang
practicality and material concerns are usually irrelevant. the lie is worth maintaining because The Devil has near unlimited time, resources, and human servants, and his top priority is Getting You
This is especially personal for me because I grew up hating my ADHD medication because I thought it made me feel like shit and not myself. Eventually, I had stopped taking it in late middle school because I felt like it was more of a burden and that I just needed to learn how to handle my symptoms. I then proceeded to have my grades dropped from As and Bs to Cs and Ds and then flunked out of college.
After over 10 years of being on my medication, I found out that it wasn't the medication making me feel light headed, delirious, and nauseous while still not helping with my concentration and attention span.
It was because I was severely dehydrated all the fucking time because no one told me that's what happened if you didn't drink water.
It's been 4 years since this revelation. I'm back on medication and drink over 64 oz of water a day and I'm doing a lot better.