While no one knows what, exactly, spurred the fallout between the evil three, most Mushroom Kingdom historians agree that Donkey Kong played a huge role in the events leading up to the division. His betrayal of Toadsworth's resistance riddled him with grief. The only thing that could make him happy again, he reckoned, was approval from his father. But Cranky Kong was horrified by his son's actions. He couldn't even bring himself to look DK in the eye. "You're no son of mine," he whispered in shame. Poor DK, he lost it.
He rushed back to Mushroom Kingdom, stricken by grief, and approached Bowser and Wario. He demanded a section of Mushroom Kingdom for himself so he could go and be alone with his torment. Bowser chuckled in disbelief, but Wario got to thinking--he wanted his own kingdom, too. The three warred amongst themselves. Donkey Kong relied on his strong, well-defined arms to bash the others, while Bowser breathed fire and slashed with his sharp Koopa talons. Wario mostly made lewd jokes and stroked his mustache a lot, which creeped the others out. In the end, the Mushroom Kingdom was divided evenly amongst them. Chaos ensued.