But because cars are major German export driver and car manufacuring is major employment in Germany, anything competing with cars has not much political support.
https://www.dw.com/en/germany-merz-pledges-to-resist-2035-eu...
That would be if kilometers of rail tracks scaled linearly with population density per unit area. My guess (based on no research at all) is it’s more that there’s a population density tipping point, and after reaching it rail development dramatically increases. I do also think you’re right about the influence of the German car industry.
Italy has a few major population centers south of dome but sparsely populated otherwise.
And so on...