They don't need to take over all of them. A dozen or two of the largest subs would be plenty. Those with less than a couple hundred thousand subscribers, don't really matter much.
As is suggested in the original post on Reddit, they could delegate moderation to the moderators opposing the blackout, as seems to have happened with r/AdviceAnimals. I feel like that's something they very well could do.
A dozen or two of the largest subs would be plenty.
Those subs required a huge effort to moderate before, but it's going to be 10x worse now that every submission is going to be AI generated pictures of spez doing things to goats or something.