"Hamas has had a large, captive pool of angry young men to convert to their terrorist ways."

More than a grain of truth here. Those angry young men are captives in two senses, first by being blockaded inside Gaza, second, by the authoritarian, grooming and twisted ideology of Hamas. The poisoned icing on the cake is that they have also suffered, in many cases for most of their lives, from the deprivations visited on them by the cruel actions of successive Israeli regimes. That all created a powder keg. This can be an explanation of what's just happened, at least in part, though in no way meant as any sort of justification for the brutality we've just seen. The angry young men in the occupied West Bank are also discriminated against but they are in no way in the same boat as the Gazans.