Historically, China has been a mostly static, agrarian nation in which the collective took precedence over the individual. It was, therefore, no great feat for Mao and the Communists to put rigorous social controls in place after 1949; they already existed in embryo.
Today’s China is a very different place–largely urban, and extremely dynamic. How do you maintain the social controls the Communist Party thinks are essential to a stable society in areas where people don’t even know their neighbors?
Through technology, apparently. That’s the reason for the cameras and the development of AI. There will be problems with the system; for one thing, the vast amount of raw data may overwhelm the reviewers, no matter how sophisticated their computers are. In the long run, however, it could work, and that’s a pretty scary prospect for people who cherish both privacy and personal freedom.