Given that rental laws in Germany can't even be broken if you buy a property for your own use ("in theory" yes but in practice...) it is not surprising why the traditional rental market is the last place someone will want to have their property

Tenant protection is good, but it breaks down in high-demand situations. And of course the better solution is to solve this on the supply side

I don’t agree that tenant protection and increased supply are comparable solutions that can be swapped out. Ideally you’d have both.

Meanwhile it is incredibly hard to build up or out in most German cities and towns due to lack of permits. Why aren't Baugenehmigungen given out? Well, landowners vote. Also, most politicians are landowners.

Lack of housing suits most people in power perfectly well. They get to control the populace through sops like the aborted rent control law Mietendeckel.