The seperatism was revived by the Communists as they realized that it was their only chance to hold onto some political power, albeit over a much smaller slice of the former Yugoslavia.
The West's ineptitude made things even worse by refusing to allow the Serbs in Bosnia or Croatia any level of self-determination while demanding it for the Muslim Albanians in the Serbian province of Kosovo. It's little wonder that so many people compare this to the 1938 appeasement in Munich.
It didn't help that this largely came to pass while the US was governed by the most unethical government in its history with a pack of diplomats as completely inept as Albright and Holbrooke.
I have been there and just wish somehow we can stop this crap once and for all. To me, raising children to kill other children over something that happened over 800 years ago is a crime in itself.
The Muslims are more guilty of this than anyone else and the Serbs and Croats are more than willing to comply. I am willing to bet that the average Serb and Croat probably is sick and tired of all this fighting also.