Football is one of the lucrative business in the world right now so if a capitalist has a enough money to buy two or more club, then all the two clubs will play the leagues but remember the players are not the same they are different players from different backgrounds so even the two clubs are paired to play a game, they will play and one must win.
And they are two things involved in such game. The players are playing for their bonuses so they will play well for their club to win and the second is they play to win the cup for the owner.