Real Madrid is only interested in Champions league and that is why you see that is their main focus and they know the right strategy in which they can use to win it most times. This is the reason why they always go for the best players a d coaches so that their chance of winning it will be higher than other clubs.
Many other clubs are just as focused on the Champions League as Real, but history has turned out so that Real is the triumphant one. As for the situation in which the strongest group of clubs is very small, this is due to outdated UEFA policies. I think that if the Super League worked (I hope this project will be implemented), then for all participants there would be a minimum and maximum budget, a salary ceiling and other measures to equalize the competition. Such a league would be more interesting and competitive than the Champions League that exists now.