"what ISIS really wants", as is the title of Graeme Woods' piece for The Atlantic, I'm afraid I want to back up from part of the main premise--that they are apocalyptic.
I'm not just looking at what Nihad Awad has to say about it, although his point about these being desperate people with no belief in worldly justice strikes me as exactly accurate. But leaving aside whether ISIS is drawing directly from Islam (and sure, maybe, enough of it is "really Islamic" but I'm not qualified to speak to that religion--I think it's more in the way Aum Shinriko is Buddhist, or the Rajneeshis are Hindu) if one were just looking at who is recruited and what they are doing, I think one would get a far better picture of what they are about than from taking their religious-flavored propaganda at face value.
A group doesn't act as proponents of violence, rape, slavery, and wholesale execution in job lots because they think its holy to do so. A group doesn't recruit from semi-criminal internet-addicted mommy's basement Jihadi-come-lately's because it thinks it has a powerful prophetic message to pass on. What they want is power, and to create zones where they have real control. They perform job-lot killings in slick videos to project that power to the kind of people that sort of thing would impress, when the glossy Caliphate pseudo-history doesn't go down for everybody. But they don't think they are heralding the end times--because really, does anyone? It's a sham.
Connecting them to the world of Islam as if they were always belonging as a kind of pernicious Wahhabism that would inevitably turn sour does strike me as giving in to their foundation myth. Cutting them off as just a cult of nutters that isn't anything like decent Muslims makes a lot of sense to me. It also strikes me that their kind of image-projection as being an advancing organization capable of real horrendous acts to prove their bad-assery genuinely requires their asses being handed to them serially and consistently. And it would be great if this was led by Jordanians, Kurds, Egyptians to further highlight what freaks they are considered by so many people who legitimately practice Islam--not by Westerners. But they aren't inextricable. They're just obnoxious. And my opinion is, the idea of the "true-believer" with this group is likely overstated. They'd like to be. But that's all. I don't know what pressure will bring out self-biting shithouse rat lurking within the org, but I believe that's what will result from a proper harrowing.