I'm not saying they didn't take control, I'm saying that the
reasons for those actions might differ from the obvious take - they were fond of buffer zones, for example (resulting in Finland being "left free" due to neutrality, though they pushed them to arm up - to prevent NATO access - or lose that neutrality). Controlled neighbours were just as good if not better as third world (aka neutral) countries in that respect. N.B. part of the conflict between Trotsky and Stalin was that Trotsky
did want to expand the revolution with military force, whereas Stalin proposed "socialism in one country".
The belief about "western capitalism first strike" was one of the major fuels for the paranoia spiral involved in soviet foreign affairs, combined with experiences starting from western support of "Whites" during revolution, through the rather belligerent actions (especially from USA) once Truman was POTUS (and well, all of Truman doctrine and its long-term effects). A non-trivial issue that shows up from reading as stuff becomes declassified is how both sides constantly misunderstood each other, leading to (in hindsight idiotic) situation where initial ideas about disarmament on Soviet side turn into Berlin airlift. Meanwhile Austrian politicians figure out how to get everyone to leave by making the country neutral. It also didn't help that in Poland we probably didn't finish burying our dead in Warsaw when USA drawn up plans to nuke it as part of nuclear first strike on USSR, plans that I have little doubt were heard in Moscow, further fueling the spiral of cold war.
So the end result is a paranoid regime (and from paranoid to controlling there isn't even a step, it's a blink) that, even when some forces try to reduce said paranoia, they stumble upon evidence that it's warranted, resulting in nobody willing to back off (on USA side, you can probably shift some proportions and replace paranoiacs with "communism must die!" die hard ideologists). In the end it's not even one side playing checkers while the other plays chess - it's two sides playing long-distance play-by-mail chess where they delegate their moves to be done by a pigeon[1].
As for propaganda - consider that both sides, to a certain extent, bought into their own propaganda, sometimes even those that should know that a specific aspect of it was false (like JFK strong arming USSR to take missiles out of Cuba, instead of admitting that the missiles were taken away in exchange for removal of the reason they were placed there - which was USA placing missiles in Turkey).
As much as the books are fiction, John Le Carre summarised it pretty well in The Secret Pilgrim although from the western PoV (but similar take could be probably pretty much taken about soviets on the average):
Smiley muses that the most vulgar thing about the Cold War was that the Western societies learned to "gobble up [their] own propaganda." The West became so convinced of the righteousness of its own cause, and the evil of the Soviets', that it never stopped to examine the ethics of its actions. In the name of expediency, the Circus opened its arms – and its purse – to every petty thug and two-bit con man who called himself an anti-Communist.
[1] Referencing a polish idiom about playing chess with pigeon - not only does it not know how to play, it will push the pieces away and shit on the board.