What nobody foresaw was that Iran would actually end up supporting AQ. The conventional wisdom was these two are completely different types of people because Iran is Shia, the Al-Qaeda people are Sunni and therefore, you know, the two would never mix. What happened in the end was that they did because they both had a common interest in destabilising the country, and for Iran I think the reason they were interested in destabilising Iraq was because they worried about having a functioning majority Shia country with a democracy on their doorstep, and for Al-Qaeda they knew perfectly well their whole mission was to try and say the West was oppressing Islam. It is hard to do that if you replace tyrannical governments with functioning democracies.
Many in the West still do not understand this today.
Thomas Joscelyn is a senior fellow at the Foundation for Defense of Democracies.