1. people suffering from PTSD who have lost much of their capacities to think clearly; specifically, part of butchered Sunni community in Iraq following the sectarian war fuelled by US invaders after years of deadly sanctions (they also include former members of Saddam's secular stasi-equivalent http://www.spiegel.de/international/world/islamic-state-file...), and some of the Syrians going through Assad's butchery. This is no different from how a bunch of peaceful villagers turned into brutal group that was Khemer Rouge (http://johnpilger.com/articles/from-pol-pot-to-isis-anything...).
2.A tiny western group who are largely clueless about the world (almost entirely about religion), seeking certain warped sense of glory: http://www.theguardian.com/commentisfree/2014/sep/04/jihad-f...
On a different note related to welfare, Saudis are probably not that worse off in certain ways: any (poor) Saudi is eligible to receive funding/stipend from his/her government for studying in world's top universities, unlike many rich capitalistic states that are effectively no less of an oligarchy.