Khamzat took Usman down after like 5 seconds in R1 shooting from far without a setup because he knew he could, his wrestling is light years ahead of Usmans. He had back control for the whole round threatening subs the whole time and throwing a bit of GnP in between as well. That is about as dominant as you can get in that position if you prioritize keeping the position (which he should, Usman should be the one taking a risk to get back up and score some points in the stand up, but he knew he would get finished and thus just tried to survive for 5 full minutes kinda like Yan vs Sterling although this was even worse because Usman was up all 4s like you said, better chance to escape). It is not really debatable whether it's a 10-9 or 10-8 when the judges ruled it 10-8 and so did +90% of the media scores.
The striking exchanges caused honestly 0 real damage to either fighter in the entire fight (disagreeing to this means end of discussion for me) but okay let's say Usman did get the better of Khamzat in the striking exchanges in R2 and R3, Khamzat landed a takedown with like a minute left in R2 and the bell rang with Usman flat on his back, probably the closest round but Khamzat edged it. Last round Khamzat took Usman down and controlled him for over half the round lol. Eventually Usman did manage to get up which is respectable honestly, but then again in the stand up neither landed something significant and Khamzat even went for the good old brawl it out ending in the last 10 seconds gifting Usman one last opportunity and he still couldn't capitalize.
I respect Usman for his resilience and defensive awareness (certainly R1), but getting kinda grapple fucked for like 70% of the fight and marginally outstriking Khamzat in like 30% of the fight (with no significant damage to either side) does not warrant a win even in with the most impressive mental gymnastics efforts.