China want there resources... US relations can be mended later...China doesn't need Putin and his regime anymore. Good relations with USA are more important as ties with a crazy dictator and his poor country
First they need water and Lake Bakai is one of the deepest lakes in the world and 200km away... China might want unending rights..
Next is gas and oil.
Then there is land... China wants some of its land back which was leveraged off them in the past...