Cain called it a "freak accident" and said that "It was just the knee, he didn’t even, like, touch me, you know?"
But I think the "freak accident" was buckling after a 6'4 sand miner from Cameroon punched him in the face.
https://imgur.com/c2o4OR5
I think like with T.J. Dillashaw, when these guys put months and months into training, (and in Cain's case, it's been really a 3-year effort to get back to the cage), have a history of being dominant and assuming they'll always win - they just can't comprehend when they're wiped out immediately and have to look to other explanations.