I don't think it's the book makers who are moving this line. From the odds history you have there, the books opened it at 1.53... Meaning they favor Volk. What moved the line could be sharp money thinking that Topuria at 2.63 could be value or maybe Volk isn't fully healthy rn. But yeah, it's weird. Best way to know is to check Volk's Insta and see what he's up to. :/
... Just checked and it looks like he's ok. He's training and promoting some stuff. Still a weird line movement tho.
Bookmakers closely analyze the performance of teams, player and also many other small details, then they decide odds themselves and traditionally stronger teams/players have low odds because they are expected more likely to win, i.e. more likely bet on them will provide outcome for casinos.
I have no clue how do bookies set their odds, but I suspect they adjust them accordingly to how people are betting. So if public perception is that Volk is on the decline (because of the way he lost to Islam) and that Topuria is on the rise, and much more money was going on Topuria - then they might be forced to adjust the odds to mitigate the risk of making losses in case of Volk's losing.
I can't say with 100 certainty either but I tried to explain above this quote. Bookmakers offer you fixed bets at first, it's not an event against other users inside particular bookmaker, so, they have to provide odds before they start analyzing of which user bets on which team or player.