Im not saying its an easy fold or anything but there are a good few hands that beat him at the river. He was reraised preflp and then checked to on a flop youd expect a raiser to bet at, especially as the preflop raise priced him in (didnt look like he was trying to be pushed off the hand). The check looks like a big hand has hit and hes looking for someone to catch a hand that will pay off.
For all his critics PH played the hand really well. If I was MM, rather than speculating on the flop I would have bet out to find out where I was.