I think that the reason for such actions by the Chinese authorities is that for many years they tried to integrate the yuan into the system of international payments and thereby expand the use of the yuan throughout the world. For the yuan already sell gold, metals, oil and so on. The International Monetary Fund began to use the yuan as one of the reserve currencies. Bitcoin can destroy all the long-term work of the Chinese authorities on the integration of the yuan in the global financial system.
The fact is that the cryptocurrency is a real competitor not only to the Chinese yuan, but also to other currencies, including the dollar. It is not for nothing that there is still very strong debate in the world regarding the legalization of cryptocurrency, because many governments believe that cryptocurrency can undermine their domestic economy.