it was a country that survived on foreign credit and was based on a cult of personality of one guy, otherwise it was very decentralized and federal government was weak.  in 1980, government didn't know much debt yugoslavia had. when they realized what sort of mess they were in, everyone scrambled to be a king in their own village and fuck over everyone else.  slovenians had nothing to do with rest of yugoslavia, besides being slavic. slovenia was a part of austria for centuries.  croats are somewhat similar to serbs, but different religion and in ww2 croatian puppet state conducted a genocide of serbian population under their control. sure, they were mickey mouse puppet regime appointed by italians with little organic support, but it happened. communist regime never conducted a proper dialogue about this, it was mostly just pushed under the carpet, and to make things even worse serbian nationalist resistance movement (chetniks) were equated with ustashas, in order to weave a nice tale about how brave communists of all nations defeated reactionary bourgeoisie scum that existed in every nation, which was a patent and brutal lie.  so resentment boiled everywhere, but particularly among serbs, who felt they were inferior in a union where they were majority. some decisions by communist government/tito were bizarre, like separating vojvodina from serbia, even though vojvodina had serb majority unlike kosovo.  similar resentment was felt in slovenia for different reasons, and in croatia.  then miloevi came to power and tried to be another tito, but failed, and then he opted to be a serb nationalist. what followed is obvious.
Montenegro