From what I understand, the ethnic tensions and lack of a desire to be unified that caused the balkanization of Yugoslavia existed during the interwar period, and the only reason it stayed together during the Cold War was Soviet support and a dictatorial government. Why didn’t Yugoslavia instead fall apart in the 20s or 30s?
/u/commiespaceinvader and /u/zwirlo have previously answered Pop history often presents Yugoslavia as a "nationalist time bomb" destined to blow, held together only by the force of strongman President Tito. But he died in 1980 and the first Yugoslav war began in 1991. What was really going on?
EDIT: This is one version of your question, but someone else may have a more precise answer for you.