Earlier quoted context omitted.
> The key here is advertisers don't want to be associated with that. Has this ever been substantiated or verified publicly? Which industry are those and why?
It's by far the most parsimonious explanation when anything halfway popular gets "demonetized". YT is a profit-seeking business, they're always going to work closely with advertisers. Content makers and users are secondary, almost nobody is paying for YouTube Red.
Well, I'd say it's a bit more than "almost nobody" [1], even if you discount trialers.