"Make your society egalitarian with this 1 weird trick!"
If we postulate that this measure will leave company profits unchanged, then the cap will send extra money somewhere else. Its backers seem to assume that it would go to the rank and file workers, but I think it likelier that the owners of the firm would begin experiencing a better return on their money. That cohort, too, is wealthier than average, though not by so much as CEOs since a lot of it is comprised of pension funds and mutual funds. In any case, the loopholes around this kind of measure are so numerous that it would be silly to pursue.
What we really need is to bring back serious inheritance taxes, even if some people want to call them "death taxes". In the long run, huge wealth is not a societal problem so long as it doesn't become dynastic. Rather than playing havoc with the incentives of the living via convoluted tax laws and weird rules, let's concentrate on fighting the growth of entrenched classes.