Michael Jackson, Bill Cosby, and Ronald Regan are all great examples of people who were considered sellouts at the time. It didn't hinder their mainstream commercial success, but there were a large number of people that definitely did not consider them cool.
Sellouts have always existed at some level, but now it's different, I don't even think a lot of kids know what "sellout" means.
> I don't even think a lot of kids know what "sellout" means.
I think they still do, but selling out to do a deal with a brand to put your name on some clothes or cookies is so far down the scale it doesn't really register to begin with. At worst, all the harm it does is a potential harm to their future art, but a man's gotta make money somehow. It is capitalism after all.
Selling out when there are moral or ethical problems in the mix, they're still able to get very mad about that, but most artists are smart enough to not sell out to Northrup Grumman, OpenAI, Nestlé, nor to your favourite local crypto coin or gambling website.
I was alert to popular culture by the time Thriller happened and I don't recall anybody thinking Michael Jackson was a "sellout". Paul McCartney and Michael Jackson did not one but two duets together.