They all do. Our Middle East policy has been consistently bad. Garbage in, garbage out. This is the best we can do folks.

ISIS started after the Iraq invasion in 2003. Disbanding the Iraqi army left hundreds of thousands of disenfranchised Sunni soldiers who knew where to find weapons dumps, knew how to use them and had every reason to be pissed off by American troops coming over.

Zarqawi saw his chance and created a book called The Management of Savagery. Basically he followed the creed of Sunni Islam that considers Shia heretics, it predates Wahhabism but Wahhabism emphasises it. Ibn Taymiyyah.. Blah blah..

Anyways those Sunni insurgents who began setting off IED's, blowing themselves up and making life miserable for everybody else are the beginnings of what later became ISIS. They successfully set off the civil war they had been after by blowing up one of the holiest Shia sites in the world in 2006. Scum of the earth.

Partly Baath party, ex saddam generals and there military knowledge, partly bad planning by the coalition which left weapons unguarded, partly medieval nonsense and gratuitous religious bullshit.