By February/March he had spent enough time thinking about crusades. Real crusades, not just 'lets clean up this neighborhood'. Well, you know, one thing is to think to think about is great contributions, but how have individuals changed history? Gengis Khan and Adolf Hitler come to mind. Not laudatory examples, but interesting. This didn't lead him very far. Did read a lot about Khan though that week.
Other crusades like health in third world etc came to mind. I read about someone who wanted to drain swamps where natives where living and were suffering from malaria. So the swamps got drained and the mosquitoes went away. And the population went up. However... the bigger population ruined their environment and a couple of generations later they were back where they started.