Zidane appears to be a few inches shorter than the Italian. That coupled with the unexpectedness of the action (as opposed to squaring off for wrestling) could have made the difference.
Heavyweight (275).
It's a long story, but I lost my spot at the 189 lb guy because I dislocated my elbow before the duals started that season.
The guy who went down from 215 to 189 was on a roll and the guy who went from heavy (he was 230) down to 215 ended up placing in state, and I could dislodge him from 215, so I was bumped to heavyweight.
I wrestled a guy who eventually went onto Ohio State as a defensive lineman up in Alliance.
I'm not saying it wouldn't have staggered him. But watch his left leg.
He kicked it out like, well I don't know what would have caused that motion.
But I DO know that this headbutt would NOT have caused such a motion without "help" from the other direction, or the player himself. Simple physics guys.