It's not about being stupid, it's about dependency and power. The offer alone is morally corrupted.
If they'd all get their equal share of money and could compete out of their own volition and quit anytime they'd want then this would be morally ok. But then nobody would watch it. And that there's exactly why this whole thing is morally wrong.
Why do they need to get equal share? This doesn't sound much different than game shows to me. People make money off of other people competing against each other to earn less money than the people organizing it. The difference is we view the contestants on Wheel of Fortune as earning it by playing a few minutes worth of games instead of whatever Mr Beast does. I don't watch his videos, I'm just piecing what it sounds like from the comments. It sounds like it could be a crude version of Survivor, Fear Factor, or Tough as Nails. People do unpleasant things, voluntarily, in the hopes of earning money.
If they'd all get their equal share of money and could compete out of their own volition and quit anytime they'd want then this would be morally ok. But then nobody would watch it. And that there's exactly why this whole thing is morally wrong.