The Bolsheviks decided those people were not needed any more. They provided the excuse for the revolution, now it had happened, no more need for the excuse.
America being more defiant by culture, might prove harder to push under in that fashion than other parts of the world.
The Camp of the Saints: Book.
Discusses at length every possible driver of the "revolution by the absolute bottom of the world's cultures," led, of course, by a few demagogues.
(In the book they all get their comeuppance)
I have not yet finished the book. I can only digest it in small doses.