Western propaganda infected minds of USSR citizens with western values. They thought that capitalism would fix their problems, they thought that Coca Cola and Mac Donalds are better than their national drinks and foods, they thought that jeans are superior to their pants. Also I think that US intelligence service funded national revolts in some republics which further undermined an Union and eventually led to its collapse and people were OK with that, because they thought that better future awaits. It was all lies. US bought Gorbachev as well, though that's a different matter, I guess.