I bought Rocket League because it had a Linux version, and Linux games were scarce before proton. Epic bought the developers of rocket League, and made it Epic exclusive. People who bought the steam version got to keep it, except for Linux users because Epic cancelled Linux support.
Epic loves to act like they’re anti monopoly, but they only care about that when they’re competing for market share. They’re extremely pro Microsoft and anti Linux.
Also one of the biggest concerns about Valve having a monopoly in the PC gaming space is that they could use their marketshare and money to block rival stores from getting popular games, making it hard to compete and removing user choice. In reality, Valve hasn’t done this, but Epic is leveraging their big pile of fortnite money to do this. It makes people think that if Epic ever gets into a dominate market position, that they’ll absolutely be an abusive monopoly that makes the market space worse for everyone else.