I think most of them knew about the West. When there was a route to escape, those who took it started pouring out, and clearly those who didn’t wanted to. I think liberalization was helped by the realization that if they didn’t, no one would be left.
However bad the Soviet economy was, there were plenty of people in the West who had good reason to make them seem stronger - for bigger defense budgets, for one thing. Plus, you don’t need a thriving economy to launch missiles. We were lucky that when the cracks became too big to ignore there was someone in charge whose reaction was toward freedom, not oppression.
The fall of the Iron Curtain and the transition in South Africa are two events I don’t remember being predicted by any sf story. Most that I can recall had South Africa achieving black rule by bloodshed.
I just remembered one. There was a novel about WW III taking place in the late '90s, written by a British general and a committee. (I can give the title when I get home.) The War ended with the exchange of bombs of two cities (Birmingham and Kiev, I think) after which the Eastern bloc collapsed much like it actually did. The authors recognized that the Warsaw Pact was papier-mâché. When I read it before the fall, it seemed unduly optimistic, but they got it right.