China's behavior makes sense if they consider both Russia and Ukraine (the latter being a proxy for the west) to be enemies of some sort. Let your enemies fight each other and waste resources while you yourself profit.

The same can be said about the US <> EU/Russia in this conflict. Why bother helping Ukraine/Europe win the war if you consider them at least partly hostile? Better to let them fight your own enemy (Russia) and trade with both sides to your own advantage.

The US considers Europe to be hostile?