Actually, it’s the anti-trust exemptions / lack of enforcement that allows the leagues (owned by the billionaire team owners) to decide who can and can’t own a team.

Otherwise teams could and probably would be purchased by publicly-owned corporations.

The NFL ownership rules prohibit public corporate ownership, although that is not due to the antitrust exemption.

There are numerous current and historic examples of corporate ownership in the other 3 leagues. Toronto's teams are all owned by Rogers. The Angels and Ducks were once owned by Disney. Comcast owns the Flyers and once owned the 76ers. CBS owned the Yankees.

That's not a hard rule; there are several counterexamples. I found the Knicks, Braves, Blue Jays, Rangers, and Canadiens are publicly-owned. The billionaires will play their money games, but they don't have full control on the entire league.