I might be completely wrong on this one but what if the Madara behind the mask is sasukes and itachis father. I know you guys are saying it would explain why he knows so much about sasuke and Itachis past if he was there from the start. When the uchia clan question itachi and he goes to kill them itachi father told him not to he listened if he was going to kill everybody anyways why would he have stopped. Also theyre father had the same basic emotions when it came to the clan and even wanted to over throw the leaf village so the clan could take control over. Why else would itachi and assure be so powerful if one was then it wouldnt be an arguement that its genetic somewhere down the line they're all probably related to madara. I think thatthe father saw the tablet and that's all it all started, and remember the time line works with the nine tail fox because the clan wasn,t slain then and also why would the leaf take the clan out if they could be takin out pretty easily. I dont know these are just my thoughts can be way off.