China just realized it's not worth betting on a losing horse. Not only Russia will lose the war that they started in Ukraine, but it will lose it catastrophically. Every day that passes, the Russian invasion force becomes weaker, and the Ukrainian forces become stronger. Today is the first day that the Russian forces started being pushed back. In the coming days we'll see this more and more. Probably in about a week or two we will see their total collapse. Ukraine will find themselves with more than 100k prisoners.
China does not mind at all giving support to a dictator. But not to a losing one.