
Religious and other cultural conflicts rose significantly after the end of larger, conscripted, close range conflicts. Globally, the massive quantity of long range, high tech, high casualty weaponry and increased surveillance allows for third party actors (religious, paramilitary, wealthy elites) to be equipped enough to incite social and political conflict.
Leaders don’t actually believe religion holds merit unless they’re followers themselves, what matters is their ability to coerce the masses and exploit power, wealth, etc. After enough manipulation, we do the fighting for them. That’s why historians are split between an “inevitable” conflict (or the opinion that conflict has never actually stopped) and a cosmopolitan solution.