Organizing people takes work, and passing off a single set of credentials to someone else doesn't mean that work will still get done - whether its all in one place or not. Look at all the subreddits which are lost because of no moderation, even when they used to have a team.

When they eventually get tired of managing all this, they will eventually need to hand the reigns off to someone else. Hopefully someone will step up, because if someone doesn't it won't matter if the group is in 4 places or one.

Which is easier - finding someone that can manage a Facebook group or finding someone that can manage his Rube Goldberg setup?

I can just give the logins to someone else. My current setup is a workable, optimal, but not clean solution to the problem.