With a solid red block extending from the Rhine to Vladivostok, the Soviets felt secure from a second capitalist assualt in the west and could afford to compromise. If all or even most of Germany had falled into Western hands at the end of the war, Trotsky would have faced far stronger pressures to form a protective "buffer" of small states. As it was, American dislike of the Nazis and the extreme thoroughness of the purges of Nazi officialdom in Red Germany gave an impression of the Soviets as Rightful Avengers rather than opportunistic land-grabbers. Remember that Trotsky never compromised in his anti-Nazi stance.
Other things that could have led to confrontation:
1.) A Communist takeover of China. I know, most Soviet as well as most Western historians think Mao had no real chance, but if things had gone a bit differently in 1946-1947, or Trotsky had changed his mind about the absurdity of a country that was still essentially feudal establishing a Communist regime...
2.) An earlier development of the nuclear bomb. If the bomb had been availaible in '45 rather than '47, it would have been a war-winning weapon rather than a super-expensive, pointless monstrosity. It was therefore possible to negociate effective atomic-weapons limitations treaties after the Soviets developed their own in '50 (plus, also, the invasion of Japan was such a bloody mess that it effectively killed off any American apetite for further conflict, and the Free Poland and Free Germany lobbies never could work up a real conflict).
Bruce