Hong Kong rejoined China under specific agreements. Those agreements were in place because the people of Hong Kong did not want to becomes just another piece of China. As such they retained high levels of legal, government and economic autonomy. Colloquially it's known as "one country, two systems."

So, yes, someone probably foresaw this issue and didn't want Hong Kong to become a puppet of China used as a giant fly swatter after re-unification.

You're probably being down voted due to the utter lack of history and context (ie: lack of basic research) you're showing which generally makes intelligent discussions pointless.

edit: A example of similar systems in the west are native reservations which enjoy varying levels of autonomy despite being part of the country they're located in.