Madara said that Obito passing through the rocks was a miracle and he just happened to coincidentally be laying in the underground passage. Kishi's answers seem to give us more questions. If Madara is telling the truth and doesn't know that Obito has Kamui and it is pure coincidence that Obito made his way down to the underground passage then I guess Madara is up to something else in the underground passage. My guess is that he's perfecting the Zetsu formula and is doing something with the Gedo Mazou. The fact that Madara's influence over Obito is just a coincidence through Obito's kamui seems like a bit of a cop out from Kishi. I would have thought that Madara would have planned to get his hands on a young Uchiha with such potential.