WI the Ottomans had been a little bit more successful in combating the Arab Revolt during WWI, and had the luck of capturing or killing many of its main leaders. Thus, prominent Arabs such as Ibn Saud, Abdullah bin al-Hussein, Emir Faisal, and Hussein bin Ali are all killed in combat, executed by the Ottomans, or otherwise removed from historical importance.
What effects does this have on history? At the very least, I think the histories of Iraq, Jordan, and Saudi Arabia would be much more complex and riven apart. In fact, there very well might not be a Saudi Arabia ITTL. What changes would this have on modern times?