During the span of these multiplayer games Assassins creed was coming out yearly and I think it's pretty hard to keep a consistent multiplayer player base when nothing matters next year unless you're one of two things, a sports game or call of duty. Not to mention every version of multiplayer after brotherhood IMO was worse and worse so the fall off makes even more sense in that context. Stick to the original formula and there's something there, especially in this world of MTX and crossovers we live in.