It's worth considering that assimilation to "German" was far from the norm in rural areas that Germans came to dominate in the Middle ages, to the extent that there were Germans in these areas, many were descended from settlers from Germany, like the Danube Swabians and the Transylvanian Saxons.

During the Middle Ages and Early Modern Period Germans came to control the Baltics, Hungary, Bohemia, Moravia, Slovakia, Transylvania, parts of the Balkans, and Prussia. The only one of these places that became ethically German in the rural areas is Prussia. I think it's a more interesting question why Prussian ethnic identity ceased to exist but not Latvian or Bohemian for example.

Hey there,

Just to let you know, your question is fine, and we're letting it stand. However, you should be aware that questions framed as 'Why didn't X do Y' relatively often don't get an answer that meets our standards (in our experience as moderators). There are a few reasons for this. Firstly, it often can be difficult to prove the counterfactual: historians know much more about what happened than what might have happened. Secondly, 'why didn't X do Y' questions are sometimes phrased in an ahistorical way. It's worth remembering that people in the past couldn't see into the future, and they generally didn't have all the information we now have about their situations; things that look obvious now didn't necessarily look that way at the time.

If you end up not getting a response after a day or two, consider asking a new question focusing instead on why what happened did happen (rather than why what didn't happen didn't happen) - this kind of question is more likely to get a response in our experience. Hope this helps!