Trust is a two way street, and the Soviets had every reason to be pissed about all the extreme anti-communist rhetoric coming out of the United States and Britain even when the Soviets were their allies.
A big part of the anti-communist rhetoric was due to the fact that the Soviet Army had not ceded much of the territory they'd taken during the way. Entire countries, notably Poland and part of of Germany, were still occupied by Soviet soldiers and puppet Governments sprung up declaring allegiance to the Soviet Union. It was clear to the West that the Soviets were not going to leave the territory they'd taken from the Germans, and the civilian populations of these countries often saw the Soviets as the new occupiers.
The west also really heeing and humming about prosecuting war criminals/nazi's put a really bad taste in the USSR's mouth. Especially since we built our entire space program around nazi scientists and technology lol.
The Russians just persecuted whoever they wanted for various reasons, real and fake. For example, hero Wilm Hosenfeld was tortured to death in a Soviet Prison a few years after the war ended on false charges. And of course the fact that the Russians also recruited Nazi scientists for the same reason the Americans did.