The 1974 Constitution gave republics too much autonomy, weakening the center.
Defying Stalin’s hegemony, Tito broke with the Soviet Union, leading to Yugoslavia's expulsion from the Cominform. This established a "third way" between East and West. Titoism & Innovation: tito and the rise and fall of yugoslavia pdf
The lack of a strong successor to Tito after 1980. The 1974 Constitution gave republics too much autonomy,