They have already done this before and they are doing it once again, I dont know what China plan yo cryptocurrency they always changed their mind in cryptocurrency and their decisions can affect the market instantly because there are so many investors in China and it makes them do panic selling.
China is a smart country so it has a lot of techniques in tinkering with the economy, so that in the field of digital currency it is very influential, they can shake the cryptocurrency market down drastically
Not that smart, but they just have a strong population that makes the market react immediately, hoping that the next time they create FUD people will be smart enough not to believe them.