Because Kabuto is a slithery snake.
He did something, idk if anyone knows exactly what, that would allow Madara to come back in his "prime".
Someone correct me if im wrong.
i thought he only modified his 'edo' body. not a mortal human body
How come he wasn't brought back to life as the old being he once was before he disconnected himself from the Mazou?
(not his edo form, his new mortal self)