Conor doesn't even know how to throw an uppercut properly. The trajectory of his uppercut is completely wrong. He had that punch flying straight up when it hit Floyd's chin. The problem with that is it pops Floyd's chin up and as the head rotates backwards, the chin escapes back too and the punch continues up without contacting the chin anymore. Basically it lets the chin escape from getting any of the weight of the punch and there is no further energy transfer into the head.
The correct way to throw an uppercut is to make sure the trajectory is upwards and very slightly forwards i.e aiming slightly diagonally up (striking under his chin). That way, even when the head rotates back the fist is still trapped under the chin and the full weight of the shot continues releasing energy into the head. You can see when boxers practise uppercuts, they rotate the punch into a circular motion which brings the punch back to their guard. At the time the punch contacts with under the chin, it is not moving straight up but instead up and slightly forwards.
You could see Conor had no idea how to throw an uppercut when he was hitting the heavy bag during the open workout. The angle at impact was totally incorrect. This is how you throw a fucking uppercut. See how the punch is not just going up but also slightly forward.
Fuck you guys there is so much technical shit that goes into this. I'm not some fucking guru, this is 101 shit with any half decent boxing trainer. This really astounds me that a so called best MMA fighter doesn't even get the basics of this. Sorry but I'm quickly starting to realise that hand striking in MMA is at a very, very low level compared to boxing.