Also: If a big hedge fund shorts a stock, expecting to drive its price down, that's cool. (Search "big short drives down stock price")
But if regular people buy a stock expecting to drive its price up, that's terrible.
Sorry, this position just isn't credible.
I don't know if it is or should be illegal but I can see why it raises some questions.
No, you're betting on the stock's future performance, not the company's future performance. There's an ocean of difference between the two.
If the company does poorly, but the stock price rises, or stays the same (Say, because we're in the middle of a COVID recession, and the printing presses are working overtime), you're going to lose a lot of money.
How do you know that everyone who bought it actually doesn't care about Gamestop's worth? There isn't really any way to prove that every single person (or even a majority of people, or really even a good portion of the people) don't care about GameStop's success and are solely doing it as a metagame.
I heard (from a non-authoritative source) that the coordination on reddit, etc. is not manipulation.