In this context, blackmailed and infiltrated mean the same thing. If I blackmail you to start changing your diet at family dinners. If we meet every week to discuss your progress, have I infiltrated your family? Yes I have.

If you want to know who infiltrated their communist government, all you need to do is look for which group of people started communism. And which group of people spread communism. It's not a hidden secret which group Karl Marx belonged to. It's not a secret who the Bolsheviks were.