Agree what was Jihad ? Roman Empire v Arabs (and others) were all involved in the same vicious conflicts long before muslims or jihad was invented.
Long before that, before the Eastern Roman Empire, there were dynasties operating in a largely flourishing and prosperous Middle Eastern region.
You might as well ask what caused christians to continue or expand the imposition of a violent Imperial Empire.
It isn't anything to do with excusing muslims. This is you trying excuse christians for their role in the Crusades by saying muslims started it.
Conveniently ignoring a thousand years of history in the process.