To clarify: Deutsche Bahn is still 100% government owned. It operates both its train service and the railroad infrastructure in fully owned subsidiaries.
And that's exactly what's not reflected in management success metrics. They are basically incentivized to steal from their owners through systematic neglect, what could possibly go wrong.
I think it's only possible to understand German politics in two ways: either nobody in politics understands incentives, or they understand incentives much better than the voters and are fully exploiting this fact.