In many European soccer leagues, the league does not control the participants in the same way. You can start a club, and start climbing to the top.

GP's not saying it negatively/judgementally I don't think, it's sort of a term of art in business finance: https://www.investopedia.com/terms/c/cartel.asp

(I say sort of because you could say it's the same word same definition just perhaps used more literally. But it certainly has a connotation to most of us that I think is how you're reading it above.)

There are plenty in esports.