Cairo-Bhagdad-Teheran - that was were its at, before they ran into the regions resource limit and adapted a religion that is great at eternal, zero-sum wars and paranoid delusions about external influence and bad at everything else.
They didn't 'run into the regions [sic] resource limit and adapt a religion'; said religion was forced upon them by the sword. Iran's state religion (if you could call it that) was Zoroastrianism. There are zero Zoroastrians left in Iran; most of them have fled to... India. And said religion ripped through the Indian subcontinent, too; it is why Pakistan and Bangladesh are separate nations today.
~70% of the current population was born under it, it's all it takes to completely destroy a nation
Ever consider that it's humans that are warped, and they abuse any institution possible for their own selfish means? Many religions fall victim to this, including those you view more favorably than Islam.