I think the NFL is more of an entrenched business with great brand recognition than a cartel. College football players want an NFL contract because they trust that the NFL will be around in 10 years. (Same reason that CS grads want to work for Google and not a random startup; Google will be around in 5 years.) This means that the NFL gets first pick on the most talented players. That is what prevents upstart leagues from being successful. Players have seen what happened to competing leagues; their counterparts are now unemployed. Without good players, nobody is going to watch your thing, and thus, the NFL will continue to dominate.
I think that with an infinite amount of money, you could probably create a new football league for a new generation. You will need billions of dollars to build 32 new stadiums. You will need billions of dollars to pay Patrick Mahomes $500M a year to switch sides. (x32 teams x53 players on the roster = 800 billion dollars a year in salary costs ;)
Because nobody has an infinite amount of money, it's not really going to happen that way. I bet you could woo a number of viewers over by having a sane online streaming package. I want to watch every game in the season for a fixed price. No blackouts. No ads. No delay.