Turpins body turned slightly to the right from his throwing his left hand just before Robby's right hand landed, Randy's head then turns violently 45 degrees with his face from the side showing the power of the punch.
The punch landed. Turpin tried turning out of the way of it and rolling with it but he still got clipped pretty solid. You can see his snap as well. After it landed Turpin took a step back where is leg isn't at full strength. Robinson clearly noticed because he immediately went in aggressively for a follow up and Turpin was
I'm still not sure. I think Turpin may have lost balance through leaning away from the punch and Robinson mistook that for him being staggered. I think Turpin would probably have gone down if that punch had landed while he was leaning back.