The British Empire, in it’s day the greatest empire in world history, in it’s dying moment as the dominant world power gave rise to JRR Tolkien. Tolkien wrote about the militant (and non-militant) forces of good militarily (and non-militarily) defeating the forces of evil, at the precise moment when the British were no longer (in their eyes) going to be able to continue to do that.
In the United States Tolkien wasn’t popular until the Vietnam War, which began the decline of the American Empire, which followed the British as the dominant global power and eclipsed them, holding half of global wealth at it’s peak. The Society for Creative Anachronism, formed during the horrors of extensively applied chemical destruction in Vietnam, honored pre-industrial society (pointedly, the age before such chemicals could be mass produced) and Tolkien, with Dungeons and Dragons following shortly thereafter.
When Tolkien moved to the virtual, “fantasy” sphere he continued the British military tradition of cleansing the world of evil for the sake of the empire (again, how they saw it).
One can’t for the most part read a book over and over again. Dungeons and Dragons was a step up in technology from books, allowing players to experience the joys of cleansing evil many times over, initiated at the time when such cleansings were thought to no longer be possible in reality.
In neither society did people stop to question whether the cleansings are right to do in the first place. So of course when the cleansings stop being viable in reality they were merely moved to the virtual sphere, and this has continued to the present day with 80% of mainstream games featuring killing as the primary mode of gameplay, usually of either monsters or “the enemy” and often in effectively genocidal manner.