This speaks to a terrible irony of the 2003 American-led invasion of Iraq. The war was premised in part on the assertion that Saddam's regime was linked to anti-American jihadist terrorists. This was a falsehood. But the invasion made this falsehood true — and in more terrible fashion than we ever imagined possible.
Haji Bakr, desperate after 2003 to defeat the Americans and the new Shia-majority government, fought alongside Sunni extremists in Iraq. Later, he began constructing ISIS. As Der Spiegel's investigation found, he was able to use his knowledge of running an oppressive security state to build up ISIS into more than just another jihadist group.