I think Tabuu is the brain of the game and the actually master of master and crazy hand because. Think of the game this was it's a kids imaginations and the the brawlers are his toys. In his imagination the kid puts his "heroes" the brawls up against all odds to save the world. After the child's heroes defeats the hardest opponent that exists (master hand or crazy hand) the child realizes the greatest enemy would be the mind (tabuu) who controls everything that can be manipulated xD Yeah sorry if none of that makes sense.