And for 40 years they could not change? Fiber is comming close and close to homes every year as it's needed for FTTC (and doing vectoring on DSL for the last 400m) and for DOCSIS on coaxial cables.
Of course they 'could', but that would mean for corruption to have gone down and political competence to have gone up in those 40 years but unfortunately it hasn't, quite the opposite.
In Germany, high level corruption and political incompetence has only increased in that time (see BER airport, VW emissions scandal, and the handling of COVID).
Basically if you're well connected and rich, you're untouchable in Germany and your corruption mishaps will be swept under the rug as casual political 'whoopsies' right after you retire to a gold plated pension.
So it's not that you're completely untouchable. Even with friends in high places.
It was written in some comments before, but Germany could have had the most modern fiber infrastructure in the world when the plans of former chancellor Helmut Schmitt wouldn't have been stopped by the Helmut Kohl government who was good friends with Leo Kirch, who was a big player in the German TV market and would rather benefit from copper wiring than fiber.