Not a moral question but Ukraine/NATO is losing the war and it's not worthwhile to fight wars that you are losing. Russia will steadily exterminate Ukrainian infantry masses and to their perspective, future insurgents unless some kind of strategic reversal happens.
China, which has the world's largest industrial base and second more powerful military is backing Russia, and increasingly open about it as of late. Of Russia's allies, they provided the most economic support. They own a lot of assets in Ukraine as well. There are signs that they are also providing covert direct military support.
China military is more powerful than all of European NATO combined and can potentially outproduce the US in a conflict.
If they get open about supporting Russia directly, Russia firepower will multiply. China uses the same artillery calibers as Russia and one of their main battle tanks uses the T-72 chasis.