The Paris terrorists didn't seem that "religious" or "conservative". From AFA: "She loved partying and going to clubs. She drank alcohol and smoked and went around with lots of different guys."
I noticed at a class reunion that that some of the extremes had flipped, like a fairly freaky urban party girl now living on a small farm far out on the countryside while some of the absolutely most boring and conservative people had flipped out. Those who just leaned one way or the other were mostly the same. I know I'm being an armchair quarterback here but it's probably the same with some terrorists, they've lived the party life but lacked some deeper meaning and purpose to their life and then had a true religious awakening becoming ultra conservative and extremely hostile towards their past life. It certainly seems to fit several convert stories I've read where they relatively suddenly become totally changed, cut off all their old friends and so on.
I don't think they're so many, but they might have a far more black and white view of the world than most. And they've probably externalized much of the blame on the "decadence" of modern society, alcohol, porn and whatnot. Apart from the violent side, many of them actually sound like pietists in Christianity - happiness comes from family, tradition, honor, worship etc. and "worldly amusements" like dancing, music, gambling, drinking should be shunned. I can sort of understand male converts who at least get the upper hand in a patriarchy, why women would want to turn back time makes no sense to me.