Why does this never happen? Well, there are many areas of the United States where real estate prices are skyrocketing even though all the houses are vacant- because real estate is being used as a vehicle for speculation. And the same thing is happening in almost every city in the western world. It’s likely the same thing is happening in Berlin. The demand is not coming from renters so allowing the price to go up does not help renters, it’s all just a tidal wave of free money from central banks looking for somewhere to go.
Also the author of the article is an Ayn Rand free-market-as-magic-bullet ideologue with an axe to grind. He makes no pretense of trying to write a balanced analysis. He even appears to be framing things like rents and real estate prices falling as pure negatives when both those things are purely positive from the point of view of anyone but a real estate owner.