That's part of it, it's also that I'm trying to find a reason why these different groups and factions would never go to war with each other unless for a good reason.

Well, you said that all of these Alts were descended from myths and legends and fairy-tales, right?  Well, don't most myths and legends and fairy-tales include some way to kill/destroy the bad monster these Alts are descended from?  Maybe they're not fighting because they know that if they start stirring things up, all the other factions know how to wipe them out.  Sort of a mutually-assured-destruction thing.  And the fact that all these stories are still around and known by humans keeps them from stomping on NYC....

Just a thought...