...can draw on a large base of people who like you don't study religious texts (even their own), instead taking the word of those leaders as being the will of god. In the Islamic world that's made worse by a large percentage of illiterate believers.
Oh, I think the predominately Christian areas of the world suffer more than their fair share of those as well, including my own country and the good ole "land of the free and the home of the brave". It's not simply a lack of literacy skills altogether which leaves people vulnerable to manipulation by those pushing agendas. Those people whose literacy skills don't extend too far down the path of developing skills at interpretation, research/verification and critical analysis are also very vulnerable