|Maybe I’m just a nutter|
ISIL is not a ragtag group of religious fanatics. They are a military force that so far have out thought and fought the best of the Western powers.
There are countries that have been accused of funding and helping ISIL. These are usually countries where Islam is the nominal faith of both the people and the leaders.
These possibly supporting countries all have incredible wealth flowing from their oil reserves.
Once the power of oil is broken either through new energy sources or by simply running out their power base will be gone.
What makes more sense:
(1) to believe that various countries with huge cash reserves are attempting (and succeeding) to recreate the Islamic Empire and trade routes that existed less than 600 years ago?
(2) to believe that a ragtag army of religious nutters has brought the western powers to despair and helplessness.