Sorry if the grammar is of, english is not my first language Because of ethnic diversity. Croatia was around 90% populated by croatians, while Bosnia had about as many bosnians as it had serbs and croats (nowadays the number of bosnians is steadily becoming the mayority). Because of this, specially the high density of serbs in what in now the Republica Srpska, the serbs did not wish to break away from what is now Serbia, which would have been a minor problem in croatia where the serb population was minimal but made for war in Bosnia (i had to research this for my thesis, but i honestly cant remember in which of my reference books it is. And my expertise is for the early modern period, so someone else will probably give a better answer.)