I don't know if that's really fair though because it's unlikely that the people that benefited from the fire sale are still the owners.

It would make more sense just enforce maintenance standards and improve renters rights. You can't really legislate supply & demand.

Still the same companies Deutsche Wohnen and Vonovia but I agree with the second part.

Their yearly profits are capped because of the Mietpreisbremse (rent control) law since all the old buildings that they bought would fall under it, so it would've been better to put the money towards either building new state-owned housing or helping the tenants enforce their rights.

The laws are there to protect tenants against neglect from the landlord but enforcement takes multiple months which is not a reasonable timeline if you have a problem in your apartment and the consequences for landlord are mostly just reducing the rent for that time by a certain percentage which doesn't make a difference if the rents are already cheap because of the Mietpreisbremse, so it would also be good to introduce fines but not sure if Germany's legal framework allows for that.