In addition to the sibling comment https://news.ycombinator.com/item?id=46012832, German(y) wasn't a state back than but a much larger common cultural term. People living in different parts of Europe would understand themself to be German, even if they wouldn't be considered to be now by their ancestry. It was simply the cultural lingua franca of Central Europe at that time, the countries were smaller and quite numerous. People used to speak German in the same way as they now speak English.

I think the mobility at that time is underestimated, it was very common to relocate to a place where the innovation happens and the other great minds were. It was more common to tour through Europe as part of the Education, than it is now. Sure a journey would take a week instead of a few hours, but you also don't relocate every day.