They are winning because they have the more compelling narrative. We don't like to admit it, but there is a huge movement toward Islam. We think we can shoot a powerful idea to death, but the people we are fighting are more committed than we are, and actually believe in the morality of what they are doing. By comparison the rest of the world has no consistent position or policy. Those who know war could see this coming when we announced we were going to "liberate" Iraq.
If killing innocent people = evil. And killing those that kill innocent people = good. How can a powerful idea, that is evil, ever attract more than the idea that is good? I don't think ISIS will ever win. Their advancements are over areas in the world that are susceptible persuasion, influence, and blind faith. These are areas that have week government, military, and infrastructure to begin with. Areas that don't subscribe (let alone are able) to ruling locally by force. It's not a surprise that ISIS has grown in Syria. Could it grow in the world? I don't think so. A world war, one with combined forces from a few countries, would put an end to it.
There's a responsibility for the Middle East to control their own. The West has learned that through endless (decades of) intervention. That's why the world, largely, waits. Liberation is only possible if it's lead by the people that want to be liberated. The border of the control ISIS can have is limited to those that choose not to fight their direct oppression.
Evil never wins. ISIS is evil. If they weren't evil they would believe what they believe without forcing the entire world to also subscribe to their ideology. ISIS is greedy, no different from "the evil corporations". That's probably the greatest irony of their reign.
