China is interested in weak Russia so that they can take its territory. They only support Russian aggression against Ukraine to benefit from the Russian isolation economically, wound Russian army, economy, and slowly digest it. Even when Soviet Union existed, they were on bad terms with Chinese Communist Party. Even Chinese hate Russian nazis.

Edit: Out of ~90 something joint non-binding agreements between China and Russia, only 4 were actually acted upon by Chinese government.

Digestion of the economy already started, among other things Russia has joined Union Pay, Chinese payment processor.