"The other factor in the development of ISIS is Saudi Arabia which is an extremist, fundamentalist, Islamic state, the most extreme in the world and far more than Iran. Furthermore, it’s a missionary state. They have plenty of resources because of the oil, so they put huge resources into trying to expand their extremist Wahhabi and Salafi doctrine by direct funding of Jihadist groups not excluding ISIS, but also by funding koranic schools." (thanks Mirvat)