There are caveats to this theory. First is the average median age of males in the general population. For Palestine I believe it is around 18 years of age. Much lower than the global population. This does imply that your theory could be correct. It also highlights one of the biggest issues counter terrorism deals with in that these jihadist groups target pre teens to indoctrinate. At the same time, no one has given a solid counter argument on how to deal with Hamas. It's not so black and white