> When 90 (?) percent of people simply lack the buying power to participate in the real estate market, but the other 10% happily sell each other estates, that's not a bubble, the real estate market just stopped interfacing with the vast majority of the population.

This. And it was not only happening in the housing market, but also in a few other markets such as arts and certain jewelry. What happened during the last ~10 years is that the huge loads of money pumped into the financial system by central banks ended up with only a select group of people, who just got richer and richer and were looking for ways to spend or invest their excess money. And that caused an inflation in the markets where they liked to spend it.