They didn't sufficiently eliminate dissent from all platforms. Information running counter to The Narrative was able to get out to the public.
He's prepping the battlefield so that during the next big thing, whatever narrative that they craft will be unopposed.
O’Brien to Winston (1984 movie/book):
“I tell you, Winston, that reality is not external. Reality exists in the human mind, and nowhere else. Not in the individual mind, which can make mistakes, and in any case soon perishes: only in the mind of the Party, which is collective and immortal. Whatever the Party holds to be the truth, is truth. It is impossible to see reality except by looking through the eyes of the Party.”