I think the idea is that Putin is a stabilizing factor (well, "better the devil you know" might be more accurate), and Russian losing in Ukraine means Putin losing, terminally.
I'm not sure that an ultra-nationalist electing to launch territory-grabbing wars aggression is viewed by anyone as a stabilizing factor. My guess is that China's realpolitik calculation is to give Russia enough rope to hang itself, then they can quietly scoop up, er, "offer humanitarian assistance to," its eastern half.