And no, it's not because of reduced taxation from rich to working class, or missing taxes on property or some other policy. These policies didn't change that much in the last decade or two. Yet throughout the last decade the state and social security systems had record income, record levels of employment and managed to run down pretty much every part of the public system from education, over healthcare to defense. The money just vanished.
I am very much convinced that Germany as a whole doesn't have an income problem, but a spending problem.