Islam gives them legitimacy to carry out whatever vile indulgence they desire, particularly against other humans. It also gives them a label for their victims so they can dehumanize them and commit crimes against them and rest well in allah.. for now. I think it may become some competitive thing as well, a way of racking up points and being superior, even in the most viscious realms of humanity.
Or, it may simply be satanic possession. The world dismisses that one with glee as fictional.. it is not.
Remember Allah = SATAN.