Karl Sharro: You want the simple one-sentence explanation for what caused ISIS?

• Saudi Arabia: financing extremism to keep a corrupt regime afloat
• US+UK: mad war for reasons unknown in Iraq
• Syria+Russia: dictator kept afloat by other dictator to keep bases in the Mediterranean
• continental Europe: Islam used as a proxy of Communism by poorly integrated youth

I must be missing a couple of other important reasons.

Iraq invasion.

There's the key issue.

--imm

... support that was necessitated from the threat to the state internally from tribal factions.

I doubt the postcolonial powers would have had much success imposing secularism, capitalism and democracy and a sense of national unity upon the numerous fragmented tribal societies within a state's boundary. These are mostly foreign concepts that would not have resonated in their culture...just as it's not taking hold in Iraq today.

If Dubya and Obama couldn't make it work in Iraq..what makes us think it would have been different immediately post WW2/Ottoman Empire?

The establishment of a Caliphate and world domination by Islam is not some new concept that ISIS just thought of. The failure of Iraq and the revolution in Syria opened the door for this to happen now but if not now it probably would happened at some point.

There's just too many cultures/religions/tribes... autocrats will always be subject to internal threats. When you have the explosion of cheap access to communications i.e. cell phones and cheap and efficient ways to organize and disseminate information i.e. Twitter, Facebook... the regime changes we've seen across the ME is not surprising.

It's easy to point the finger at Bush but there's a lot more going on here to consider.