Berliners vote to expropriate large landlords in non-binding referendum

Isn't buying existing stock wrong way to solve the problem? Shouldn't the money be spend instead to build new stock thus increasing supply? Providing under-market rate housing to some people just removes it from elsewhere increasing prices for rest and eventually pushing the rents in general up...

Some additional information not in the article:

Berlin is one of the fastest growing cityies within Germany, adding around 60,000 new citizens every year. Historically, it has been a very cheap city to live in, but this has been changing quickly, with more and more parts of the inner city becoming too expensive for working class people. Berlin is also the fastest growing state economically within Germany, wage-wise as well, but this is uneven growth, with unemployed, elderly and working class people being left behind. Anecdotally, wages in the tech industry are really good for the living cost, with people being able to pay as little as a fifth of their income on rent, while people making below average income often have to pay up to half of their income in rent.

Berlin's public finances have always been terrible, and in the early 2000s the then-conservative government of Berlin privatised large amounts of public housing. The flats targetted by the referendum now are actually largely those privatised 20 years ago. Public finances are better today, but still not great, so critics of the referendum claim that it is unaffordable and will lead to a new debt crisis. Proponents say that the cost will be amortized over 30 years through rent income.

The referendum also specifically states that the real estate companies would be paid significantly under market rate for these flats. Anecdotally, this made quite a few people switch to voting in favor. Realistically though, this would be unconstitutional, and thus not get through the courts review process.

The bigger parties in Berlin have come out majority against the motion - the Left party and the Greens are in favor, the social democrats, conservatives, neoliberals and Far right against, but it is important to note that Berlin is governed by a coalition of red-green-red.

On the same day, we also voted for a new federal government and new state government, and in both of those elections Berliners increased their votes for parties on the left of the political spectrum.

Lastly, it seems like quite a lot of people didn't understand the core of the referendum, at least there were a lot of reports of confusion about it. Polling also suggested much less support than the final vote, so it might be the case that the result is biased in that activists all voted yay, while people unsure or just slightly against simply abstained.