There is a premise in the "selling out" scenario that assumes the artist is accepting money from a company so that company can sell more of the same -- or even a WORSE -- product using the artist to market the product. This CAN be true, and humans have a cogitative bias to remember negativity over positives. So we remember the times when the artists screwed over their fans... and hence we boo them.

When marketing collaborations are used to inform people of something actually good, then they can actually be great for everyone. The best example is Ben & Jerry's Ice Cream collaborations. It's hard to communicate "no, it's hard to understand, but this blend of candies is especially worth trying," so the best way to do that is to have a celebrity vouch for it. And, what do you know, those collaborations have been wildly successful. It's hard to convince people that "putting ice cream cone in the ice cream" is surprisingly good, but if you just put Stephen Colbert on the label with a big thumbs up, most people will give it a try.

Marketing can be manipulative, but it can also be very, very helpful to customers who don't have perfect information. This is exactly the point of Rory Sutherland's book Alchemy: https://www.goodreads.com/book/show/26210508-alchemy