While I just believe that all the OP said was his guess on behalf of the Chinese government regarding the ban on bitcoin based on his confession which I quote below.
Everything is my guess.
OP, as a Chinese citizen, it's still possible that you don't know exactly what your government's goals are behind the bitcoin ban. There are a lot of thing they don't reveal to the public when you are completely controlled by the government. I don't believe that your country's government doesn't want anything from bitcoin until they decide to ban it. If they want to prevent fraud and keep their people from losing their investment, then ban it in my opinion is not the right solution. I feel there is a hidden purpose to the bitcoin ban scenario in China that has yet to be revealed. I know China as a communist country whose government really want to control everything.