Well, if the Mazo was summoned then that means that Madara, who was hooked up to the Mazo, would no longer be, therefore he would die. Then obito would never have been evil and there would have been 0 plot to naruto.
He was waay to young to do any of that. Even when his parents died he didnt summon the mezo he only summoned it when yahiko died and that was shortly after obito introduced himself to him.