Ok..so that proves that the all of these invaders mustered army at the name of religion quite easily and motivated them to invade kaafir for the sake of "Islam". It fulfilled two purposes "plundering the wealth" and "slaying kaafirs to spread terror of Islam" .... . Even if these invaders were not religious freak ,the army was religious freak and quite enthusiastic in plundering and slaying of the "kaafirs", Venomous Islam!
So if plundering was the main purpose , religious purpose was also not far behind!