Public good refers to the concept that governments can override the needs of the individual in the interest of the majority. Now that doesn't mean that the public good is necessarily "good" when that strategy is employed by the State, it's just an excuse to control and submit. There's really not much good associated with it. It's not based on reason but on sacrifice. Xi justifies the draconian policies by arguing that it's in the best interest of China ie the public good to pursue certain policies. And while the Chinese people witness a continuing rise in their level of prosperity, they're subservient enough to play along. When the Chinese economy falters, then the people will be a threat to the State. So Xi is setting up backstops in an attempt to prevent this should the economy fail. Nice.