> hoarding of real state and making it a miserable investment.

Homeowners are a powerful voting bloc and do not want this. Many EU states also have excessive rent control, which creates another powerful voting bloc who also is opposed to any change in the housing market.

There is only ever one problem that makes housing too expensive: zoning restrictions that make it illegal to build huge volumes of cheap housing. There's a huge amount of evidence to support this, and very little evidence to support any other theory. Even in towns with a lot of tourism and AirBnBs, the problem is a lack of hotels (which are almost always superior to paying a cleaning fee and then having to clean your room yourself).