A lot is cultural and historical. In fairness there is blame to go around. If you look at the history of relations between the Catholic states that bordered the Orthodox countries, it is one of incessant hatred and on again off again war. Poland the Teutonic Knights and the Hapsburg Austro-Hungarians all had a long history of waging war against Orthodox countries and religious repression of their Orthodox minorities. When Russia eventually became a major power and was able to push back, they gave as good as they got. Even today there is a lot of bitterness in the lands that are effectively the border between Catholic and Orthodox Europe.
Interesting, I had a conversation with a friend from Croatia that mirrors what you said. You know any decent books or websites that discuss that Orthodox vs Catholic tension?