I didn't say they have held it for decades, I'm saying they own the exclusive rights for the next couple decades (I think it was a 25 year exclusivity period, which they are now ~7 years into).

There's nothing stopping an unaffiliated race series from starting up, but good luck attracting any top tier drivers.

Organizations unaffiliated with FIA can do whatever they want. There are not many of them though. Even American motorsport is affiliated with FIA [1] even if I think that the link has been very weak for most of its history.

One problem surfaced as many times as Formula 1 teams threatened to break away from FIA and do their own league is that FIA could ban all FIA seriest to race on circuits that organize races for the break away series. That's bad for circuits because they lose many weekends of income so nobody wants non FIA series.

[1] https://en.wikipedia.org/wiki/Automobile_Competition_Committ...

It is the internationally recognized body responsible for motor racing, so you would have a very very hard time convincing anyone to take you seriously.

There's obviously nothing stopping you from setting up your own series, but there's a _lot_ that would go into it, and the FIA handles a lot of that stuff for other series.