But you won't have shown a causal mechanism in any case.
Are you referring to causality between religion and war/terrorism, or the idea that 90% of terrorist attacks being Islamic-based has nothing to do with the doctrines of Islam itself?
If it's the former, then there isn't a 1:1 link. You can have war without religious issues. The most bloody wars in history and the cold war that followed had nothing to do with religion. Religion's certainly played a part in wars, but it isn't the be all and end all.
If we're disputing the former, I disagree. The idea of the Middle East being a playground for Western empires has been brought up as if that explains everything. I'm not denying that the ME was carved up after the collapse of the Ottoman Empire and that the borders are artificial, but that doesn't take into account the prevalance of terrorism in Africa and Asia, most of which is still Islamic-based. We don't see similar levels of terrorism from other religions.
I'll skip ahead and posit as to why. The first is that the Abrahamic religions are far more zealous than a lot of other ones. Noel Harrari explained this better than I ever could in
Sapiens, but what he posited is that when your religion is based on the idea of one supreme god that shan't suffer others, you have a vested interest in stamping out any other competitors. He contrasted the lassire faire approach to religion in the Roman Empire (when it was polytheistic) as compared to the more dogmatic versions of Christian rule that followed. This has been made most apparent in Christianity and Islam in that both have displayed a zeal in converting people into the faith that most other religions haven't - the Zoroastrian praying to fire isn't particuarly interested in the faith of those outside his tower for instance.
The second question then, is why Islam? The argument I've seen, and one I agree with, is that Christianity takes its very name from Jesus Christ, while Islam takes its faith from Muhammad. Jesus preached peace and tolerance, Muhammad spread his faith by the sword. This isn't a spiritual discussion, the Arabic conquest that followed the rise of Islam is well documented. Christianity, despite all the attrocities done in its name, does have the idea of "loving thy neighour" and turning the other cheek, which is why it's been posited that we don't see similar levels of Christian-based terrorism. Islam, on the other hand? Not so much. There was a book that pointed out, using Indonesia as an example, that if we believe that religious terrorism is a response to oppression, then there should be much more Christian-based terrorism in Indonesia. But no. Instead, it's still mainly Islamic, despite that faith already having a special status (de facto, if not de jure).
So, yeah. Even if you factor all the geo-politics in the world, Islam still has more terrorist acts done in its name than other religions. The more fundamentalist you get in Islam, the more violent you become (as opposed to Jainism, where it's the other way round). You can criticize Western imperialism all you want, a Chechan Muslim beheading a French teacher over depictions of their prophet is not something that can be called geopolitical. ISIS killing people in Vienna isn't geo-political, because as far as I'm aware, Austria hasn't played any role in the Middle East.