There's an unfortunate game theory to a large civilization in that it requires hard work, ethical behavior, and deferral of gratification to build. But then eventually people start to forget that and think "why would I work hard when theres all this stuff here already? I should just be hedonistic". Slowly, the civilization starts to decay causing it to take care of people less, which causes more people to defect ("why should I take care of a system that doesn't care for me? Especially when there's so much fun to be had by neglecting it"), until eventually it collapses because everyone has defected.
it's getting harder to show up for work each day knowing there are unemployed men in Colombia with 3 girlfriends doing motorcycle wheelies at 2 am