I thought I read a British analysis that they didn’t expect that submarine to be “economically repairable” – that is, Russia would have been better off just building a new sub at that point than repairing it.
The kicker is that Russia absolutely did not need to base that submarine there. They didn’t gain military advantage by doing so. Like, it was a “look, I so fully control Crimea that I can park ships at Sevastopol” thing. This is on Russia choosing to make a symbolic move.