You have to realise what a strong PR campaign you're fighting. The media is inundating us with the narrative that these are religious nutjobs sprung forth from the well of Islam, doing everything because of religion, and ISIS (or whoever is responsible for their superb western-style PR) is doing the exact same thing. We have all this excellent snuff porn to go along with it as well, professionally shot for maximum bloody bloodiness, pretty much exclusively for our benefit. I haven't watched a single one, but I'm sure they're guaranteed to evoke an incredibly visceral response.
It's a potent mix and people are falling for it hook, line and sinker. I mean, when you have barbarians willing to mass decapitate people for your viewing pleasure, that's a very powerful storytelling tool.
The complex geo-political narratives - the fostering of terrorism and violence in the middle east through quasi-Western support, the brutalisation of the middle east, the overthrowing of governments, the funding for ISIS coming from the likes of Western allies Saudi Arabia and Qatar - these are far less sexy stories, far more baffling stories in light of the prevailing narrative, and most people don't have the energy or the will to take a long hard look at them and their deeply troublesome implications.