an interesting hypothesis. i think the following factors also contribute.

people who come to power by the use of force are not generally diplomatic, or willing to compromise. they want to keep their grip on power, but are constantly afraid of losing it.

for this reason, their energies and intellect are consumed by their quest for control. they see their own survival as the baramoter for success. in societies where there is great religious and ethnic diversity, this as a recipe for slaughter.