People want something easy to blame. They don't like a large mass of party officials that have no name they might have to step out and research. It's why few people in the US get angry at Congress and more just name drop Obama. Gorbachev was the leader, that's the leader that everyone knows. That's who gets the blame.

It also doesn't help him that he has remained active in political and social commentary on many hot button issues at a time when many russians are feeling nostalgic, renewed, and angry. Nationalistic fervor is high and all they're remembering is that people used to respect the dead empire it was, but now small countries they used to hold dominion over leave their sphere of influence every day.