That was really the line of thinking in large parts of the US-government for a while.
Best expressed by no one else than Harry S Truman, who, when a member of the congress complained about the huge amounts of former Nazis in the new intelligence agency the US was building up in post-war Germany (nowadays known as BND), simply replied: "I don't care if this Gehlen guy
[first head of the agency, a former Nazi-general] is fucking goats - as long as he's helping us, we'll use him".
During the 2nd world-war, if you played your cards well in Germany, you could achieve a lot. Some people early on realized this and built a career on it that often continued after the war. If you had the support of "the system", you had almost unlimited resources at your disposal.
Von Braun used these resources because he had a vision, a dream - and he was crazy and ruthless enough to sacrifice anything to make his dream come true.
Like the above mentioned Gehlen, he was also bold enough to change sides when the right time had come - knowing that the work he had done and the ideas in his head were more interesting to the Allies than the rest of what had happened during the war.
People from the UK (where V2 rockets hit mostly) are usually furious when you mention the name - they'd have probably wanted to put him up for trial in Nuremberg and seen him hanging - but his work, his men and he himself were already too important by the time the court was setup - and the cold-war had already started.