1. Usyk was so much bigger than Biev so he could withstand the punishment better, and he still was knocked down. Bivol is not a natural 175, he’s a blown up 168. I don’t think he’ll be as durable as usyk against Biev.
2. The amateurs are tailor made for Usyk and Bivol’s style, Biev has always had more of a pro style (emphasis on power and accuracy instead of output) which is why he never won Olympic gold imo. Usyk barely outpointed Biev in a scoring system that favored his style. Just because Usyk beat him in the amateurs it doesn’t mean he would’ve beat him over 12 rounds (back then).
3. Usyk has much better lateral movement than Bivol. Bivol has fast feet but it’s mostly in and out of range, Usyk has much better circular and lateral movement, changing angles, etc. Much harder to cut off the ring against Usyk than Bivol.
4. Usyk had the punch to keep Biev off him, we’ve seen Bivol enough to say that he isn’t a big puncher. Dude hasn’t knocked anyone out in almost 6 years.