Popular attitudes could have shifted, as apparently they have in the Donbas, after nearly a decade of Russian rule. However, subsequent opinion surveys suggest otherwise, though it is difficult to measure public opinion in an autocracy. Absent a showing of popular support, Kiev cannot justify destroying Crimea to save it. Of course, the disposition of Crimea would be a proper topic for peace negotiations, which could include providing for an internationally monitored referendum to determine its status.
https://www.theamericanconservative.com/leave-crimea-alone/
https://www.theamericanconservative.com/leave-crimea-alone/