You are right if many players hit their maximum limit at the same time and win, then theoretically the casino could be in trouble. But why doesn't it happen in practice? Casino games are designed in such a way that the player's chances of winning are always lower than the casino's. The more players there are the closer the casino's overall result gets to their expected profit. That is even if some people win a large number of people will lose which ensures that the casino pockets a large profit even after paying out the winners.
The way gambling is wired, the chances of winning is a lot lower than the chances of losing.
Just imagine that you make like ten selections while gambling, you as a gamblers must have 10/10 for you to win that your bet, while the casino is just hoping for a single bet inside that ten selection to fail, so the casino will always be the biggest winners or benefactor in the gambling arena, that's why I believe that the casino will always have the capacity to make a huge payout of any kind to any one that won, if they are truly genuine.