No dominant religion in the Middle East? Haha!

The reason is fractured is because of the inherent tribalism within the cultures of the region. Strip away the tribalism (Oman, Qatar, UAE to an extent), concentrate the people near a few cities (Egypt), or provide them a unifying overarching culture (Iran, Turkey), and you get some success. In fact, the early Islamic empires were heavily mired in infighting even though they were "unified" under the Caliphate, in spite of the Prophet's calls for the "Ummah" (One Islamic Nation). I would even argue that Islam's biggest contribution to the region was in providing a specific administrative framework with which to shed the tribal infighting and unite culturally similar but disparate peoples together. It's also why Israel succeeded as a nation with its European flavor of nation-state identity.

An Israeli intelligence officer perhaps correctly attributed it to the past culture of water scarcity and needing to protect your water sources. That is, in the desert, there are only so many sources of water, and if someone steals it away from you, you simply die. So that created a culture of inherent suspicion of outsiders and people outside the clan, even though they all share the same customs and culture.