Germany had a great train system but Germany also has a big automobile industry that spends a lot of money on lobbying.

In the end of the 90s with neoliberalism being very popular, it was decided to privatize the trains. The effect was only minimal investments in the infrastructure and a gradual rotting away of the train network. Now we a reaping what we have sown.

The enshitification of the German trains was done on purpose so they don't compete with cars.