They didn't create ISIS? The main reason ISIS thrived when it did was circumstances. Like Assad ruling Syria Saddam Hussein rules Iraq as a minority Sunni ruling over a Shia majority. When the US invaded and overthrew him the inevitable happened and the Shia majority took to ruling Iraq. However just like elsewhere certain Sunni's rebelled and so formed ISIS.
Now remember the Republican Guard the highest trained and elite group which kept Saddam's grip on power and was identified as the only part of the Iraqi army worth worrying about. Well they were all Sunni's and so ISIS benefited from much better military knowledge and experience then the Iraqi "Shia" army they were fighting. Hence the Sunni ISIS were able to defeat Shia generals who had never had Saddam's trust.
stating the US created ISIS is just not factual. Indeed by invading Iraq the US did much more for the Shia side of the eternal Shia v Sunni struggle. Indeed now that the US has allowed Russia to help Assad to victory and not blocked Hezbollah's power in Lebanon a Shia stratosphere of influence exists from the Mediterranean to Afghanistan. It that power that has the Saudis worried, and funding anyone fighting the Shia Iranians be it in Syria, Yemen or Libya.
