Earlier quoted context omitted.
Well in recent months the Tesla Giga Berlin factory has shown just how fast construction can take place if the people in power actually want it to happen. Building new housing units in the city slows the increase in value of existing real estate, which is why property owners are not rushing to allow the construction of new structures. Lobbyism is a powerful force in real estate.
To be fair, it's not he people in power it's the construction companies. The amount of workers on a building site in Germany is way lower than in other places. And then you get the ones where they put 2-3 people for 2-3 weeks every 6 months.
Public construction on the other hand goes with the cheapest bidder, so doesn't pay that well. Also, the state will only pay after a lengthy process of inspections and trying to find something wrong with the finished building. So lots of companies just avoid public bids, because they cannot afford to finance all the materials and work pay for the duration of the build. Those that can afford it are companies that specialize in public construction sites, usually designed to be able to go bankrupt at the first sign of trouble.
Generally, in a public construction site, all contractors are lowest bidders. Some do intentionally bid lower than cost to get the contract. What they then try to do to recoup their cost is to try to find some problem that wasn't spelled out in the bidding, or to wait for some change of plans or regulations. Because they then can bill a lot more for the additional work and material necessary to fix the problem, or hold up the construction site in lengthy court proceedings. Because everyone knows that something like that will happen at some point, they intentionally go as slow as possible, waiting for the order to drop everything and wait for the courts. Because if they are quick and invest a lot of work and material, they might not survive the delay.