It's very obvious to me, given the information contained in the last three chapters, that there was more going on between Oro and Madara than we all previously thought.
Oro was CONSTANTLY looking for an uchiha body.
i believe he, not zetsu, was the one who found Obito in that cave. Or fuck it, maybe it was Zetsu, but either way, Oro was the one responsible for putting his body back together. Who besides Oro (at a time when tobi for all practical purposes, doesn't exist yet) was capable of such expiraments? Oro and Oro only.
Now, Oro was definitely planning on keeping this body for himself, because a body at least partly Uchiha was better than none at all. But somewhere in his experimentation, things went wrong.
This could have to do with DNA experiments done on Tobi's body with Madara's DNA, that I'm not sure. But if he in fact is Obito, Madara would've been long dead. He sure as hell didn't find him.
Could it be that when Madara was dying, he left a piece of his consciousnesses with Zetsu (if he even existed then) to store into the appropriate body when the time presented itself?
All I'm saying is the only ninja with the medical knowledge to put a half smashed body back to life at that time was Oro. He obviously wanted it for himself, but something happened to make that impossible, and a piece of Madara's soul was implanted instead.
By the way, will a mod move this to the theories section for me? Put it in the wrong place like an idiot..