And that's what so baffling, they already control the Supreme Court. They have the votes to pass any other nominee off the Federalist Society list (and as the head of said organisation says, anyone on that list is as good as the next one as far as solid conservative credentials are concerned). And yet they purposely choose to stick with Kavanaugh.
It's either down to them wanting to send a middle finger at the Democrats, or the specter of Bork's failed nomination is still haunting them, in the same way Nixon's resignation does, as something that must never be allowed to happen again.