Why did Rome fall?
Rome fell because the city became so corrupt politically, economically, and morally that its own internal decay defeated it. No outside power had to conquer it; it destroyed itself from within. The context presents this as an example of a society collapsing when it abandons moral restraint and religious values.
Les explains that Rome had the greatest military machine of its time, yet the city itself became so corrupt politically, economically, and morally that nobody had to come in and whip them. Rome defeated itself, and Rome fell. He connects this to a secular writer's point that unless a society is guided and controlled by religious values, it cannot last; even a religion one disagrees with supplies behavioral guidelines. Without restraint, anarchy prevents a society from lasting. Historians warn America is going down the same road and will destroy itself from within, not by an outside power.