The root cause may not be too hard to figure out as the Saudis are currently in an overt anti-Shi'ite mode, not only decimating Shi'ites in Yemen but in their own country and in Bahrain. Now they have picked on Qatar because that state was getting to uppity and actually dared speak to Iran. Now ISIS is inspired by Saudi Wahhabism and, like al Qaeda and other Sunni terrorist groups, is funded by Saudi Arabia.