I think religion is just camoflage. I think that there is a certain subset of humanity that just likes to kill people. They will be attracted to whatever movement allows them to satisfy their urge. Think Nazis, the dirty war, Charles Taylor, Bosnia ad nauseum. There never seems to be a shortage of people willing to torture and kill. There may be people in the heirarchy that have a larger plan/purpose but the rank and file do not seem exclusively or even primarily motivated by religion