Seems a bit megalomaniacal.
"I'm not interested in doing this any more. Therefore I'll shut it down for everyone"
This way, people have been given plenty of advanced notice and can start their own forums somewhere instead. I'm sure each of the 300 subforums already has some people running them, and they could do the above if they actually cared.
I find it hard to believe someone will take over 300 forums out of the goodness of their hearts and not start making it worse eventually, if not immediately.
Nonsense.
And since social media works the way it does, you can also expect a ton of unaffected people to also pick up their pitchforks and join in without having any real clue what's going on.
And that's assuming there isn't some law somewhere that really does put you on the hook for it.
300 forums is a lot of power.
It makes a lot more sense to expect the sub-admins of those forums to start their own communities elsewhere than for just hand power to a single person over all of them.
Yes, that's possibly 100 middle-aged men you could urge into battle!