Why did the assassination of Franz Ferdinand lead to World War I when other crises in the Balkans had not? What were the mitigating background factors?
Answers (1)
I am not aware that anybody ever actually knew what caused WW1. A Serbian peasant murdered an Austrian duke in Yugoslavia, so Germany invaded Poland. And that is about the clearest explanation you will find on the subject.
We are forced to conclude that it was religious: the whole continent was possessed by a spirit of bonkers.