I think it's the opposite - that any of them were a viable possibility. I feel like for whodunnit movies, most viewers don't want some big "out of left field" twist to be the answer. They are given multiple possibilities that all makes sense along the way, and you just don't know which one it is.

If you are given all those options throughout the movie, and then none of them are the answer and its something else entirely, that would make the rest of the movie seem completely pointless imo.