People were afraid of their own country. Without a happy populace, any country will fall apart.
Take, for example, England's many revolutions, especially the one against Charles (the fifth?). He was silencing people, imprisoning people, cheating people. So they took down the government and set up a new one even though England's economy was doing good.
Also, all the crap Russia was put through with Czar Alexander II. He did such horrible things like freeing the slaves (serfs, whatever), setting up local governments, and allowing Russia to become more like Europe. So what happened? His people killed him.
The Soviet Union would not have lasted.