At first in the cave-to-cave rivalry, they bashed each other to death with rocks. Then they advanced to clubs, knives, swords, spears, arrows and guns. Their holy and/or political reasons for murder evolved from hunting territory, family loyalty, tribal pride, religion, nationhood and conquest.
The historic list of absolute rulers go from Saul, Hannibal, Pharaoh, Caesar, Napoleon, Hitler, Mao, Stalin, Kim Jong-un and, just maybe, Trump. Through it all, the basic urge of humanity is still to destroy other humans by whatever means are available at the time.
While we were still in its primitive state, Saul and Caesar had only spears and swords to use for mass murder. Unfortunately for today’s humans, the current brain-challenged leaders have immensely more effective weapons, literally at their fingertips, that can destroy the planet. So, while threats escalate, will it soon finally come to the familiar final lament: farewell cruel world?