In the course of the Arab Spring, the legitimacy of many ME leaders/dictators was questioned, among the most notable of these was the rule of Bashar al-Assad of Syria. A popular local outpouring of resentment against his regime was coopted and inflamed by hardline Sunni extremists, many of these being veterans of the Iraq War or younger generations of recuits. This escalated into a full civil war, which quickly turned into a proxy battle for control over Syria, which heretofore had been a Russian proxy state, with a large air base.
While the United States has been arming anti-Assad (who also are notably anti-American) forces, Russia has been targeting civilian population centers (with both conventional and chemical weapons) to first create then inflame the Syrian refugee crisis, driving political instability first throughout Turkey then the EU - both sides seeking to ratchet up the pressure on terms favorable to them.
The tl;dr is a civil war turned proxy war is creating some of the most acute human suffering present in our world today.