After the collapse of the Ottoman Empire, the area that we call the Middle East started to destabilize. The decline of the empire gave something of free rein to nationalist impulses in the area. Most importantly, it allowed both Arabs and Jews to have nationalistic ambitions.
Immediately after the Ottoman Empire split up, Britain took control of the Levant under a League of Nations mandate. Both Arabs and Jews wanted to have self-government in this area. During Ottoman times, these ambitions had been suppressed. However, the British encouraged them to some degree. This culminated in the creation of the State of Israel and the conflicts that arose between it and other countries (like Jordan and Syria) that had been created out of the ruins of the Ottoman Empire. In this way, the collapse of the Ottomans allowed the conflict we now have in the Middle East to arise.