"but to what end?" Obviously, Ukraine can collapse the Russia economy and military production sufficiently that Russia can no longer effectively fight, and take back all the occupied territory. In the long run, it doesn't matter what happens inside Russia it their economy is in ruins and they can't afford to fight. How they deal with that is their problem. Anyway, the problem isn't Putin, it's Russian society: they're genocidal imperialists who have been invading their neighbors and taking land for hundreds of years.