The reason why many Serbs turned against him was that Serbia was impoverished by sanctions and war while the West promised prosperity if they vote the "right" way.
No, the reason that Serbs turned against him is that they realized that he was nothing but a communist who had destroyed their country for his own benefit. Oh, and lets not forget the internal repression and political assassinations commited WITHIN Serbia during his rule......
There was widespread opposition to him even before the Kosovo war. He was attacked for rigging elections in the 90's.