So I was digging around some weird ideologies for my timeline, and I found this one called "nationalism," basically the gist of it is that people who are linguistically, culturally, and ethnically similar should unite under their own state. Like, a german empire other than the HRE or a slavic nation taking up the western Balkans. Obviously, this didn't take off too much otl- I don't think Austria or the Ottomans could survive if it were more mainstream. But why didn't it?