Note: these are just my thoughts on the matter. I was born in Yugoslavia, but the only thing I experienced were American bombs. My views were formed by research and talking with people from different countries who lived through most of it.

The fall of USSR was definitely a factor, but I don't think it's nearly as important as you're making it out to be. Also, Stalin was the reason why Yugoslavia's planned economy was fucked and why it had to take western money to survive. Don't get me wrong, the western influences were definitely a factor, but there was a lot more going at the time.

The whole federation was held together by a cult of personality, nearly nothing was done to resolve internal issues and nationalism, and there wasn't a sensible plan on what to do after Tito. That gave western agencies a route to sow dissent.