We could chalk that up to them trying to legitimize themselves. Their branding is Islamic and their language seems Islamic.

But their hearts have duality. We know the ISIS soldiers who are caught have extremely little knowledge of Islam and Quran. We know the bathists from Saddam's party many of them are high ranking dude in ISIS ranks. They kept ultra religiousness at bay when they were in power. Being part of ISIS is a power game. Our prophet (pbuh) has warned us 1400 years ago about a savage group of people who will appear in Iraq. They will call to truth but they will be liars at heart, they will recite Quran but it won't go past their tongues, meaning it'll be all talk and no substance or adherence. Our Prophet(pbuh) mentioned these people will go outside the fold of Islam as fast as an arrow pierces through the game.

I also see ISIS having a very particular agenda which falls in line with a very particular agenda of the US foreign policy. 2007 Biden introduced and the senate passed that bill where it was decided to cut up Iraq in to 3 nations. Thanks to ISIS, there is now a Kurdistan, Isis and Iraq. CiA doctored the Syrian uprising. These 1st rebel groups were trained and armed by the coalition. Isis is looking to take down Assad, another policy supported by NATO. No action is being taken against black market oil buyers.

Russia seems to be the only one who is actively hitting ISIS where it hurts, so much so that a NATO country, Turkey took down a Russian Jet for the most retarded reason. I suspect the oil and weaponry routes were under threat which cause Turkey to commit an act of aggression against a UN member state.