It is easy to manipulate ignorant, unhappy, dispossessed, and resentful people. It's like throwing a bone to a starving and excitable dog. You cannot blame the dog in such a situation, but the cynical villain who throws him a bone to gain his attention. In this case, the cynical villain is NATO, and an Islamic State is the bone that NATO and its bought and paid for Sheikhs have thrown to starving and mad dogs.
The Salafist/Wahhabi dogs now have the idea of an Islamic State in their minds, they have latched onto this bone with all their will, and they're not going to let go. They will bring Syria down with them, killing religious and ethnic minorities throughout the process, and NATO and Israel couldn't be happier.
Video - FSA Demonstration in Syria Calls for Establishment of Islamic State & Extermination of Alawites [Source: Eretz Zen].