If the government has already been disrupted, then who is taking down the Internet?

No, the goal of “take down the Internet” is to degrade the organizing of protestors / agitators / insurgents, while preserving the ability of government to organize against them. It only works if the government has a separate sufficient infrastructure, or completely controls routing on shared infrastructure. Neither of those are true in the U.S.

To pick just one recent newsworthy example, the federal government does not have a way to deny Signal messaging to their opponents, while preserving their own use of it.