Naitch
Reads history books
The Sherman act is about a monopoly crushing the competition and creating an unfair playing field.
NASCAR directly owns a good portion of the venues. The CARS tour has never tried to compete with NASCAR (and good reason), I can’t imagine NASCAR would be very friendly with them if they did. The singular existence of a “competitor” doesn’t negate a monopoly.
You used to be able to take old chassis and run in other series. You can’t do that any more. That’s a huge barrier to entry for any prospective league.