Do you recall when the Mountain does that powerful leg swipe at an unarmed Oberyn, and the Prince just cartwheels over it? I said before, that Mountain revival bit looked so fake, and makes no sense considering the injures he had. How does he even roll over on Oberyn with an Achilles that torn? Not to mention how fucking calm and he was during his kill. One minute he's dead like , the next minute he's like the undertaker coming back to life right when John Cena starts yapping on the mic.
It could be argued that Gregor making contact is fair because Oberyn was being a shit and not even looking at him at the time, but as soon as he felt his leg being taken from him, theoretically there are many things he could have done besides taking a fucking pratfall. Seriously. Look at the clip of him falling and you see he jumps up in the air to the point that it's mildly comedic. He should have had a way out of it before Clegane got his hand around his throat.
The Mountain getting the advantage and going on top of him could easily be a combination of adrenaline and playing possum until he saw a clear opening for a counterattack. As soon as Oberyn dies he collapses, so it's not like he totally no sold it.
I know it's dumb as hell to be so upset over, but the fucking trip and the way it completely fucked Oberyn just kinda ruins the whole scene for me in terms of credibility.