As you quoted yourself, this is among all creeds, not among muslims. France has larger muslim population than germany or GB that were in the same survey, yet this still does not explain the huge difference in youths actually supporting daesh. So, its fair to say that french youth in general is disillusioned. Also note that this was before charlie hebdo and the recent attack, not sure how the non-muslim french would respond now.
The banlieues are often referenced , but were the terrorists from the banlieues? the whole thing seems to be orchestrated from belgium.