After the war, he was sent back to Northern Europe as commander of the DP camps, under UN auspices. Once again he involved himself in aiding Masaryk against the Soviet agitators. Remember that Czechoslovakia was nominally still a Republic at this time. However, because of Yalta, the Czech Republic types were snubbed by the State Department and left to fend for themselves. The only support to be gotten was simply to get people out. Masaryk was pushed out the window, he didn't jump, and the fall of the Czech Republic was assured, as the rest of Eastern Europe. They let it happen because it was policy, and to be honest with you, my Grandfather said it was FDR's policy, because he wanted to show Stalin that "we mean't him no harm". It was appeasement of a different sort.
You can say the Red Army had overrun Eastern Europe and the deed was already done. But the intentional revocation of support for Czechoslovakia, The Baltics, and Hungary tell a different story. They were intentionally left in thrall to the Communists because of balance of power calculations and Communist influence within both Cordell Hull's and Dean Atcheson's State Departments, with the acquiescence of FDR and Truman.
I grew up with a man who was there for the whole thing. Everyone in my family always called it a sellout. You can show me all the links and documents you'd like, but I'm afraid I'm a little firm on this. Roosevelt was after a balanced world in the aftermath and I don't think he thought Communism was all that bad. He got his balanced world, but at a 50 year cost of freedom for the people involved.