In the wake of that Turkish reform the Arab states became independent (after a decade or two of French and British colonial rule). After World War II (1939-45) rapidly growing demand for oil (which Arabia had lots of) made many Arab states (especially Saudi Arabia) quite rich. The Saud family had taken over most of Arabia in the 1920s and formed a kingdom for the express purpose of safeguarding the primary Moslem holy places in Mecca and Medina. The Saudi royalty tried to use this to become the leader of Islam but found that most Moslems politely ignored them. There was no denying the huge oil reserves (the largest in the world) the Saudis had, and gradually that became quite a lot of power.
While the Turks and Saudis (and about 80 percent of Moslems) were Sunni, the Iranians (and ten percent of Moslems) belonged to the Shia sect (which conservative Sunnis considered heretics). In the 1980s Shia clerics in Iran managed to form a religious dictatorship and proclaimed a worldwide Islamic revolution (which most of the word, including Moslems, ignored). The Shia clerics in Iran saw themselves as more worthy guardians of the most holy religious sites in Mecca and Media. The Saudis, and most Moslems, did not agree.
The Iranians are still at it and are being quietly supported by Turkey (a traditional and ancient enemy). Although Turkey has been ruled by a moderate Sunni Islamic party for the last decade, the Turks don’t feel they should take sides in some Sunni-Shia conflict. Saudi Arabia and other Sunni Arab oil states feel threatened by a militant Iran. Turkey sees itself as the only adult power in the region and deserving of resuming a major leadership role (without the old imperial burden of actually administering and policing all the people in the region). The Arabs are not keen on this, as they have bitter memories of the harsh Turkish rule. There’s also the ethnic factor. Islam was created by Arabs and while all Moslems are supposed to be equal, many devout Arab Moslems believe they should be a bit more equal.
The Turks are trying to demonstrate their new statesmanship by achieving peace in Syria without enraging the Iranians or handing Syria over to Islamic terrorists. The Saudis feel the Turks don’t know what they are dealing with. The Syrian rebels would appreciate some more Turkish help in overthrowing the current pro-Iranian Syrian government. The Turks are reluctant to get too directly involved lest Arabs get upset over a return of the old Turkish (Ottoman) Empire in the form of Turkish troops in Syria. Currently the Turks feel the Syrian government will eventually fall. The Arabs would prefer to see this happen sooner rather than later. But, unlike the Turks (who have one of the two, next to Israel, most powerful military forces in the region) the Arabs are unable to just march in and overthrow the Syrian government. This rankles the Arabs but it’s just the way things are (and have been for a long time).
So there you have it. Turkey, which has and could again dominate the region, doesn’t want to do it via force. Iran, which wants to turn all of the Middle East into part of its new Islamic empire, doesn’t have the military might to do this. Decades of sanctions have left Iranian forces weak, which is why Iran is so eager to have nuclear weapons. The Arab states have not been a major military power for over 600 years and are nowhere near to regaining the power they had in the distant past. Reality, resentments, and unrealistic aspirations all conspire to create what passes for politics in the Middle East. All this misdirection and posturing also tends to give the Islamic terrorists a free ride and a degree of sanctuary. For centuries it was customary to shelter rebels and terrorists from neighboring states and try to use these zealots as one of your own diplomatic and military tools. The more lucid zealots figured out how this went and sort-of went along. Think of it as another local tradition that just won’t go away.