Is it just me or did the movie feel far too rushed? It felt like there was enough material here that if they wanted to they could have made it into half of a season rather than just an hour and a half long movie.
According to the Director, the Author of the Light Novels that the animes are based off of, Kamachi Kazuma, had enough written material for the plot of the movie to easily make the equivalent of two whole seasons but that was obviously impossible and way too much and they needed to find a way to cut it down to a 90 minute movie. On top of this the movie itself was a essentially 10th anniversary celebration so to speak and they also still needed to get all the characters from both Railgun and Index in there as much as possible. The Director also stated that he was very proud because they were surprisingly able to get almost every major plot point in there in some way even if it was only hinted at, but they just never went in too deep with it. So, you are absolutely right there is a lot more to the plot of the movie however it was always intended to be a 90 minute movie because it exists only as a 10th Anniversary celebration and as an original story not part of the Light Novels and they were forced to cut it down it's just that the author of the light novels is a bit of an overachiever.