You're right about ISIS for what its worth. The documentary "The Power of Nightmares" is a really good introduction to the background of that whole story for people who criticize you on the topic. Its very accessible and well researched (and from the BBC, so reputable).
But yeah, the short and long of it is that Donald Rumsfeld specifically disbanded the Iraqi command structure after the invasion, against President Bush's orders, because he believed (correctly) that it would result in large groups of them forming armed militias and start a middle eastern uprising. His belief, thanks to the teachings of his mentor Leo Strauss, was that without a mortal philosophical enemy the United States could stay at perpetual war with, the US, buoyed by continued economic prosperity, would continue drifting towards liberal ideals like economic, social and racial equality, and away from things like duty, honor, and fear of god; which in his mind, made America great.
In short, they believed the fear of communism is what kept Americans in line, and that the progress of the 60s, once that fear started collapsing, was something that needed to be avoided at all costs from occurring again. So they needed a new enemy, even if we had to make it ourselves.
Rumsfeld even, at one point, came out and explicitly said that that was his goal at the time, so its not even a conspiracy. Its publicly stated fact, that gets little to no news coverage.
Its like when Dick Cheney came out in an interview over the biopic he published, and admitted on air that the reason he was for torturing people [paraphrased]: "had nothing to do with intelligence. If we tortured suspected terrorists, no one would ever be able to call the Republican party weak on terrorism". He literally admitted to a war crime, and nothing happened.