1. They’re pissed with the process and don’t want Democrats to “win” by sandbagging then digging up some provocative allegations at the end of the process.
2. They’re on team Republican. Kav not getting confirmed feels like losing, and no one likes losing.
3. They’re afraid that if the nomination gets pulled, something similar could happen to the next one. In the unlikely event Democrats take control of the senate (I’m told this is a historically bad cycle for the Dem senators based on the seats up for election) another extended delay after Kav could mean 8 SCOTUS justices until at least 2021.