We're going through a period now, the dark ages where teo or more sides have come into serious conflict. This is just a temporal state until we can settle are differences and let the past go. You have to realise this happens in every society. Europe had to go through that period and fight each other to near extinction in order to settle differences between the powers, nazy germany, imperial france and britain and later on communism too.
There will be people i nIraq who want to settle scores over the injustice caused over the last 2--30 years. A power grab is an issue too.
Ultimately we need to evolve as well, one aspect of modernity which is essential for a civilisation to go forward is to let go of the tribe/clan metality. Run society based on merit. We have too many cleptocracies in the Muslim world (countries run by families) and power brokered out to their own tribes.
This is something that is essential for us, and I think like the commie once said "eggs need to break to make an omlette".
Prophet Muhammad (saw) broke time tribes and unified the arabs. But just a generation or so after his death the tribes rememerged. We live in a more educated world right now, ther eis more transparency and channels for communication. I think we will overcome our issues.