The original Assassin's Creed included a co-op mode, but it was cut because it clashed with the game's storyline, Assassin's Creed 3 mission director Philippe Bergeron told OXM in a recent interview.
"Before we knew about the Desmond story and Animus link, we had a huge co-op component in there," Bergeron said. "But it just became too hard to do: the engine couldn't support it, and then the metaphor we had above it didn't support it. Co-op was one of those big things at the beginning that just didn't make sense in the end."
That's because, according to Bergeron, it was impossible to reconcile multiplayer within an ancestor's memories.
"Your ancestor lived his life in a certain way, so assuming you had branching storylines, it creates a paradox," Beregon said. "It didn't fit."