The root cause of it is not nationalism. It's economic troubles and loss of allies. Yugoslavia had an insane amount of debt, and they had too much liberalization of the market. Playing the middle ground between the two global powers was not a good strategy in the long run. They also actually had a cult of personality (not saying it's necessarily a bad thing in our case, it had its use), and of course it all crashed after the personality was not there anymore, unlike the USSR (referring to Lenin/Stalin), Cuba (Castro), etc. Nationalism just came out and offered it self as the main "solution". Now I'm getting into whataboutism but I really highly doubt anything like this would have happened if Yugoslavia did not completely economically collapse in the late 80s, as there would not be that level of dissatisfaction and the need for an alternative solution would also not come out, as painfully as this at least. Basically Yugoslavia probably needed a cultural revolution, but Tito was not that guy lol