I mean we never learned anything about him once Obito used him at that one time to kill the mist anbu and jonins, isn't it strange? Off topic, I realised that Madara probably hasn't read the whole Uchiha tablet. When he read it, he only had EMS, he hadn't acquired rinnegan which means that he couldn't have read the whole thing. After all he was very old when he got it and there is no way he could have gone back to the leaf in his current state, after all he had to be connected wtih the Mazou in order for him to keep living.