While Arabs maintain their longstanding ethnic majority in the Middle East, it is the non-Arab states—Turkey and Iran—that are the region’s most powerful Muslim forces. Asher Susser explains:
The last two generations have witnessed the steady decline of the Arab states, to the extent that some no longer even exist as the unitary entities they once were, like Syria, Iraq, Yemen, and Libya. Generally speaking, the Arabs have not modernized successfully. Most Arab states (excluding the oil-rich and less populous Gulf states) suffer in one way or another from a critical imbalance between population and resources resulting in consistently poor economic performance. . . . The erstwhile movers and shakers like Egypt, Syria, and Iraq are but shadows of their former selves. . . .
The void left by Arab weakness has been filled by the non-Arab states of the region. . . . Iran and Turkey, as opposed to most of the Arab states, are not recently established entities and unlike many Arab states are not artificial creations, but large countries of some 80-million people each. They have long histories as sovereign nations, with unique linguistic and cultural identities of their own. . . . Turkish and Iranian nationalism has consequently proved to be considerably more cohesive and politically successful than Arab nationalism.
Arab nationalism, especially in its revolutionary Nasserist formulation, was the panacea that promised the Arabs renewed power, prestige, and prosperity. But it did nothing of the kind and turned out to be a false messiah. . . . [And while] Arab nationalism sought to supersede religious sectarianism in the Arab world and to unite all the speakers of the Arabic language as one nation, Islamism had the opposite effect of exacerbating sectarian differences.
For the Islamists, religion was obviously the key marker of collective identity. In the Islamist worldview there were very clear and meaningful divisions and distinctions between Sunni and Shiite Muslims and between Muslims and non-Muslims. As radicalizing Sunnis and Shiites highlighted their [disparate] identities, various non-Muslim minorities were left with little choice but to withdraw into the protective sanctuary of their respective communities. Arab societies broke down into their sectarian components, eroding the integrity and cohesion of multi-sectarian Arab states.
Read more on Dayan Center: http://dayan.org/content/changing-regional-architecture-middle-east