As much as I hate Bitch McConnell I do enjoy his autistic game of passing everyone off. What he gains from it all I don't know.
Frontline did a documentary on the politicization of Supreme Court nominations a couple of years back after Kavanaugh got put on the court. Ironically, a good chunk of the documentary was spent, answering that question.
The documentary's answer was that Mitch McConnell was BFFs with Robert Bork, who infamously had his nomination to the Supreme Court squashed by Democrats as "revenge best served cold" payback for his role in the "Saturday Night Massacre" during Watergate (TL;DR Nixon kept firing Attorny Generals until he got to Bork, who did as he was ordered and fired the special prosecutor investigating the Nixon administration).
Mitch was furious when the Democrats basically destroyed Bork's judicial career via the confirmation hearings and relitigating Watergate and Bork's role as Nixon's hatchetman, culminating in the Democrats refusing to approve him for the Supreme Court.
When several years past, and Clarance Thomas was up for nomination, Joe Biden infamously led the charge to "Bork" Thomas (Bork entering the political lexicon by that point meaning "to be denied political appointment to high office over your past") via the charge of sexual harassment.
For Mitch, this was both a repeat of the Bork debacle and worse, as it showed the Democrats resorting to dirty pool of the most extreme kind to try and kill a SCJ nomination. Hence why they fought like the devil to foil Biden and the Democrats schemes.
Which turn led us to 2008; Biden's now VP and McConnell has risen to top guy in the Senate on the GOP side. Needless to say, at least according to Frontline, McConnell going full obstructionist was partially due to Biden and wanting payback against Biden and company for what they did to Bork and Thomas