This is the main point here I think. "Casual Racism" (for the lack of better term) is widespread in Eastern Europe. People there use racist rhetoric all the time but they themselves *surprise* don't find it offensive (since it's not directed at them) and are very nonchalant about it.My girlfriend is from an eastern European country. She told me she would expect the people in her country to not understand why blackface is bad if asked, but that was BECAUSE racism is so ingrained there that they don't see a hugely racist action as problematic.
This is the root of why people "don't understand", not because they don't understand racism, but because they don't see the problem with racism.
It's very similar with anti-Semitism and some measure of support for neo-nazism/fascism. I do know folks that recently came from over there (Russia, Ukraine, Belorus) and yeah, racism is very much a thing still there at a level where people don't even see it as being quite wrong (at least regarding some bad terminology, concept of blackface and so on).