Both Saudi Arabia and Iran have been trainng and radicalizing their different branches of Islam, and their proxy wars are the worst kind as they are based on extremist religious beliefs. Many of the non-extremists and members of minority religious sects have fled these proxy wars and are now refugees, as well as much of the professional class. This leaves the extremists even more firmly in charge. Saudi Arabia and Iran both have a lot of blood on there hands. The US has some partial responsibility, by first helping to install the religious extremists who became the Saudi Royal Family (it was about oil), and second through massive long term military support.