Manhattan Project? Infiltrated. Hollywood? Infiltrated. British Foreign Office? Infiltrated. West German Chancellor's Office? Infiltrated. Your high school locker room? Heh you know it
What made Soviet intelligence so good at subverting and infiltrating every fucking organization on this planet?
I think for awhile they could recruit intelligent people who were also idealistic about communism which is international in scope. It wasn't just about money or whatever (and they didn't have any money). Bolsheviks were also by nature conspiratorial and believed in combining both "legal" and "illegal" methods for the pursuit of their aims which developed out of the conditions of pre-Soviet Russia. Their strategy was a kind of dual-power seeking where they'd target non-communist groups (which may not have been previously considered as vectors for political activity, like theatre groups or whatever) for infiltration and subversion. Cadres are basically like agents who get inside other groups and try to maneuver them in some kind of way rather than the Communist Party showing up and being like "we're here now!" That's more like after a coup d'etat led by communist infiltrated organizations including the military.
<Read "The Organizational Weapon."
They infiltrated everything but still lost the war