If you know anything about Germany between 1933-1945, you will know that Nazism permeated the society. That doesn't mean every German supported it, but in many ways it was like Communism in the USSR. At a certain point you had to at least pretend to support the Party to get where you wanted to go. This article talks about the German Rocket Scientists in Huntsville and alludes to their Nazi past. If you want some more information see The Paperclip Conspiracy by Tom Bower which starts thusly "As the giant Saturn V rocket rose majestically through the morning sunlight from Cape Canaveral in July 1969, two groups of German scientists beamed, flushed with pride." It also says "Twenty-five years later, the Americans were reaping the benefit of their youthful genius, however neither von Braun nor Strughold willingly discussed the circumstances in which the scientific origins of their work had materialized...their craft,..had been realized amid the calculated murder and brutal butchery of Nazi atrocities." (p. 1-2).
So, they were not as pure as has been made out to believe. The issues of post-WW II Europe drove the Americans, British and Soviets to recruit these scientists and harness their abilities.