There is a small group of actors that benefits from these projects. The bribery part is hard to prove, I give you that, but it is very likely.

Bribery isn't "hard to prove" but instead there are no credible bribery accusations at all. Missmanagement in massive infrastructure projects are a much more reasonable explanation. It also makes a lot of sense because the actors are often state government officials that have never overseen a comparable project. Planning an airport or a new flagship concert hall is difficult. I agree that there were serious mistakes but they can be very well explained by incompetence rather than bribery.

And this cluelessness is then abused by contractors. With flanking maneuvers targeting political leadership. No clear cut corruption, but the lines get blurry.

Fun fact, for a very long time German companies could declare bribes paid abroad in their taxes. Legally. Seems that a lot of people didn't get the memo that bribery was, indeed, illegal now.

> Fun fact, for a very long time German companies could declare bribes paid abroad in their taxes. Legally. Seems that a lot of people didn't get the memo that bribery was, indeed, illegal now.

Surprisingly realistic policy, considering that bribery is simply part of everyday business in some locales.

Of course they would, in some places it's just the way business is done. At least if they declare it, you can plan for it when executing projects abroad.

Why would the management of a massive project be given to a group that has no experience with such a massive project?

There's a podcast on this. "How to fuck up an airport". The short answer is that all the bids were realistic-ish, and therefore too high for the budget. So the Berlin politicians went "We'll do it ourselves! Much cheaper!". And lo and behold...

Any number of reasons. Maybe they had the lowest bid?

Well, it’s not hard to mismanage something especially if you want to mismanage it.

There have been multiple corruption cases surrounding BER which also explains the level of incompetence at display here.

You are correct regarding the BER, apparently there have been some corruption accusations I didn't know about!