ISIS and the modern, westernised girls who flock to it

The premise outlined in the title is all kinds of inexplicable. While trying to grasp the whole wtf aspect of it, this old quote from George Orwell's 1940 review of Mein Kampf stood out:

Also he has grasped the falsity of the hedonistic attitude to life. Nearly all western thought since the last war, certainly all "progressive" thought, has assumed tacitly that human beings desire nothing beyond ease, security and avoidance of pain. [...] Hitler, because in his own joyless mind he feels it with exceptional strength, knows that human beings don’t only want comfort, safety, short working-hours, hygiene, birth-control and, in general, common sense; they also, at least intermittently, want struggle and self-sacrifice [...] Whereas Socialism, and even capitalism in a more grudging way, have said to people "I offer you a good time," Hitler has said to them "I offer you struggle, danger and death," and as a result a whole nation flings itself at his feet.