I dunno, maybe because people are stupid

“The First World War is a mystery. Its origins are mysterious. So is its course. Why did a prosperous continent, at the height of its success as a source and agent of global wealth and power and at one of the peaks of its intellectual and cultural achievement, choose to risk all it had won for itself and all it offered to the world in the lottery of a vicious and local internecine conflict? Why, when the hope of bringing the conflict to a quick and decisive conclusion was everywhere dashed to the ground within months of its outbreak, did the combatants decide nevertheless to persist in their military effort, to mobilise for total war and eventually to commit the totality of their young manhood to mutual and existentially pointless slaughter?” – John Keegan, The First World War