A wage cap isn't possible and definitely not fair for the players. If Messi generates a club attention worth 200m annually, he deserves his share of the cake, like it or not.
Truth be told, people, countries and companies can do with their money what they want to do. That is freedom. And if an investor thinks it makes sense to spend gazillions on a club then that's his choice.
What should actually be fought is the corruption usually associated with these investments. I once read an interesting article about how Abu Dhabi seeks political influence with their football investments and that some shady things have happened in these contexts, former politicians being hired by their companies etc. That's the stuff that has to be prevented and investors will sooner rather than later stop spending more than they get out of the clubs. Drain the swamp.