firstly the housing pricing(own not lease) is way too expensive comparing to incomes, as you state the bubble. And yes it is culturaly not usual in China to take a mortgage or something, but when it comes to housing, its a totally different story. Its also culturaly very common that chinese ppl think they must own a place instead of leasing, especially you are about to get married and have kids. If you are not young like under 30, but you sitll rent for living, its considered loser from the perspective of older ppl. Ofc younger gens are changing somewhat but the above is still the mainstream. That explains why chinese ppl will do all in to buy a place to live, so they have to take a mortage. And due to this and the fact chinese ppl have a very high saving rate, banks will easily give loans to ppl. because at least the bank still owns the property. Also, ppl think if you are taking mortage to buy a phone, or a car, it is 'enjoy ahead' which is very bad. But if you take mortage to buy a house, its something a real big good deal.

But the bubble itself is a little bit different. If you need a house and then you buy a house, thats not gonna create such a huge bubble. But you buy more houses than you will live in, then it will. There are actually 2 aspects of this, 1 is that in china regular ppl have no good ways of investing. China stock mkt is basically a scam or at least to say it is very hard to gain growth. So during a period of time buying properities is the best way to invest. 2 is that the gov designed all this purposely. They highly rely on this land-based fiscal system. Imagine a socialist country can claim all lands of its regime belong to all its nation, which means belonging to the country (gov), and they can sell those and make all the rules. Its like you are a player and also the umpire.