The Soviets dominated mathematical research; the West only caught up when the government collapsed and the Soviet mathematicians emigrated to the West.
I haven't read your link yet, but I understand soviet maths developed more-or-less in parallel isolation, with some innovations on both sides - about what you'd expect. Non-isolation would have yielded greater progress.
(edit: spelling)
So, I don't think von Ardenne - who worked on nuclear projects, not rocketry - or other German participation is as big as what von Braun's team has achieved.
By all indications, von Ardenne worked on quite a few projects, and it is quite interesting that the Soviet Moon project that ran when Germans were allowed to go home, ended in nothing much more than a few spectacular explosions.
The point where we started was that Soviets pioneered the space travel and remained - up no now - comparatively quite good at it. I'd attribute that both to good decisions made at the foundation of the industry - and to lack of commitment to space advancements on the West especially after Moon race and end of Cold War in general.
Of couirse it's not like SOviet space rocketry ewxisted in a vacuum, completely separate from ballistic missiles either. Gagarin's rocket basically was one of the early ICBMs. Once they realized that making copies of B-29 will only get them so far, they threw all the effort into rockets instead. Space program was a side-effect.
Orbit-capable rockets were for a long time being developed for military goals, it was only governments which can afford them and governments had their own justifications. In USA, for example, a lot of military rocket technologies found their way into civilian NASA programs.
At least after Stalin's death they stopped claiming that pretty much everything has been invented or discovered by Russians (with an occasional Ukrainian or Uzbek thrown in for good measure).
>As Sergei Korolev was said to have joked, the guards who protected him in his high position as the chief designer of the Soviet space program were probably the same ones who watched over him in the sharashka.