I came across this interesting question on Reddit today. I think Budapest would be much more multicultural if it hadn’t been for Trianon. As a result of the Treaty of Trianon, Hungary, as you know, lost a large part of its territory, along with numerous communities of different nationalities and cultures.
If this dramatic change hadn’t happened, Budapest would probably be an even more diverse, multicultural world capital today. The population of the city would be richer, as the various ethnic groups and languages would only enhance this diversity – they were, after all, parts of historical Hungary. Cultural diversity would have also contributed to richer art, more diverse cuisine, and social dynamism.