The “one child” policy was based on the Paul Ehrlich “Population Bomb” theory that human beings’ need for resources would eventually overwhelm the supply, and create scarcity for everyone. It was part of the Malthusian school of thought. Now, of course, it created sex imbalances (because of sex selection and the cultural preference for boys), a potential pensioner / GDP ratio issue, and all sorts of other problems. Communism, eh?
The Polymatter channel has a pretty good three part series about why the Chinese are so desperate to create a hegemony now. If you want to read about what may be the beginning of the debt problem, look up Evergrande on any financial website (or in the news).