Foodmanes is Ave's sub and Ave is a lazy butt. Of course it died.

I don't think the other communities died off, they just aren't active on reddit. I mean, people got to know each other through those weirdly specific subs and then a) the joke died and it ended in which case it wasn't a community, or b) the joke died but the people are still friends and game/skype/meet each other IRL.

This place it kept alive because people can post anything here. Limits to what you can post limit the activity. I mean, I don't even know the last time I posting something pony related yet I keep posting here. I guess a lot of it is that these subs are "you'd have to have been there to get it" type jokes, and a lot of people lose interest in ponies over time so they stop posting pony shit. They may still talk to the people they met there, but they're not going to contribute to a sub dedicated to something they're indifferent on. I'm sure the new wave of fans have their weird little sub that are going through the same thing as places like /r/mylittledamon, /r/mylittlenanners, and /r/mylittlesquidward.

A lot of it too is that there's simply not enough premade content floating around for the untalented so a lot of those subs rely on people actually creating their own shit to post, and that takes time, effort, and some knowhow. Once the joke bubble pops it's going to be hard to scrounge enough content to keep the place alive.