China is looking after their own interests, but they absolutely don't want their largest export market to struggle. The global economy is not a zero-sum game, and the idea that it might be is the root of many of our policy issues in the US.

Chinas interests today are a US with reduced power and a global economy more focused on China.

Someone loses power for someone else to gain. It’s literally the definition of a zero sum game? China targets areas it thinks it can win and dominate in the future.