Lots of speculation on Twitter about this—a failed attempt to re-open all closed subreddits and instate their own moderators. I can't imagine it'd be that, although I do enjoy the conspiracy, and more likely they were using the window of reduced traffic to make some larger changes and they went awry
I can't imagine it either, though it wouldn't be outside the realm of some of the stupidity that has gone on. But it would almost certainly be the death knell for the site - those subreddits who didn't "go dark" now would.