In The Prisoner's Dilemma, the point is that the best option (Both Cooperate) only works if people are willing to work together. It almost always ends up in the worst option (Both Defect). What this points out is that purely selfish actions can lead to non-optimal results for both the collective and the individual.

This expands on The Prisoner's Dilemma by increasing the population and increasing the stakes. We're still thinking about cooperate/defect actions, but we're also forced to acknowledge that not everyone is a rational actor and we cannot relay on the all-defect option as would be the expected outcome of The Prisoner's Dilemma.