You've been following cryptocurrencies for a long time, and understand that accusations of bitcoin for burning large amounts of energy arise all the time. And then suddenly China decided to start a fight against it.
Therefore, I still did not find the answer, why does China need it?
Suddenly? You don't seem to be following the development of the situation when it comes to China and crypto mining. Here, read what is written in the article from 2019.
On Monday, Chinas central state planner, the National Development and Reform Commission, included cryptocurrency mining in a list of 450 wasteful and hazardous activities slated for elimination...The proposed ban, which was originally reported by the South China Morning Post, could come into force after a public comment period ending May 7...The proposal, if enacted, could take time to have much impact, says Katherine Wu, an independent crypto industry analyst. She notes that this is different from past cryptocurrency clampdowns, which took more direct action.
China has been against Bitcoin from the very beginning, or perhaps better to say from 2013/14, but for some reason it has decided to gradually ban it, instead of ending it in the short term. However, this decision is not just about Bitcoin, many other activities have already lost or will lose the privilege of cheap energy - elimination has been announced, it is just happening - and those who took the warning seriously have long relocated their miners.