Comment by anovikov

Just like in Soviet Union's case, trick isn't how to topple a regime, a sufficiently rotten one will fall by itself, but how to make sure the country that remains is sufficiently neutered to not become a menace again. It was simply overlooked by the West in 1991: they foolishly fell under the influence of their own propaganda and believed that Communism was the problem and with it gone, there was nothing left to worry about. As it turns out, Russia itself, was the problem. It was easy to solve in 1991 and extremely hard now. Hopefully it won't be repeated with Iran.