Board Thread:Naruto Discussions/@comment-27615170-20170519084657/@comment-734582-20170603181415

Obito wasn't under the full force of the boulder. The center of the boulder (where it rests on the ground) is a good distance away, so Obito was only partially covered and wasn't nearly as badly crushed as it seems.

Plus, Madara or Zetsu almost certainly intervened in his survival, keeping him alive through the ordeal even when he should've died. I mean, Madara found him in one of his tunnels? How the hell did Obito not get the boulder further on him when everything collapsed? Well, we have seen that Zetsu can easily move through the ground and can infest people without even expert sensors noticing. They can also transfer chakra easily. Plus, they were keeping an eye on the area.

So, Madara lied: Zetsu saved his ass.