>Original not released in USA so no one knew about it
>terrible marketing
>strange concept and hard to convey to the audience
>terrible cover art
>first person RPGs seen as graphically primative compared to FF6 or Chrono Trigger
>no tv ads as far as I know

The most obvious is that the original wasn't released, so there was no hype for the sequel while there was in Japan. The marketing barely showed off screenshots of the game, or the characters, instead showing taglines about how the game stinks or smelly objects not even in the game.

The cover art should have been NESS with a bat and his friends fighting enemies to convey the adventure and combat, like the cover of Chrono Trigger did.