Oppressive governments are constantly in fear of their own people. The Communists promised people prosperity and if they can't keep the economy going (aka "food in people's mouths") then people will revolt. It's not as simple as "order the military (which is also the people)" to kill all of the people. China is totally dependent on their relationship with the rest of the world and if they openly slaughter half of Shanghai then this will inevitably be condemned by the rest of the world. They will face sanctions, meaning no foreign resources. All their foreign support will dry up because foreign powers will know the Chinese government does not have support of the people. China's enemies will stir up revolts everywhere to burn shit down in blitzkrieg-type attacks until there is no infrastructure left.

And how are those Chinese soldiers going to feel when they find out all of their and their families' life investments no longer exist? How can Beijing be sure that the soldiers stationed at all of the posts along Chinese borders will not (in their poverty and discontent) start abandoning their posts or accepting bribes to let foreign soldiers in, etc.

Ultimately, as an organization, China cannot exist without the cooperation of its people.

Oppressive governments are constantly in fear of their own people. The Communists promised people prosperity and if they can't keep the economy going (aka "food in people's mouths") then people will revolt. It's not as simple as "order the military (which is also the people)" to kill all of the people. China is totally dependent on their relationship with the rest of the world and if they openly slaughter all of their own people then this will inevitably be condemned by the rest of the world. They will face sanctions, meaning no foreign resources. All their foreign support will dry up because foreign powers will know the Chinese government does not have support of the people. China's enemies will stir up revolts everywhere to burn shit down in blitzkrieg-type attacks until there is no infrastructure left.

And how are those Chinese soldiers going to feel when they find out all of their and their families' life investments no longer exist? How can Beijing be sure that the soldiers stationed at all of the posts along Chinese borders will not (in their poverty and discontent) start abandoning their posts or accepting bribes to let foreign soldiers in, etc.

Ultimately, as an organization, China cannot exist without the cooperation of its people.