^^That explanation does seem more likely. The burden of leadership is getting to Rick.
Frankly, I'd rather watch Walking Dead evolve into a show about a community trying to rebuild than watch endless cycles of the living fighting each other and the core characters moving to a new "safe haven" every season.
Maybe it's realistic to think that humans would be ridiculously paranoid and untrusting of each other, but the only way humans are going to avoid extinction is if they rebuild communities. We don't need to see more flashbacks or explanations for the how and why of the apocalypse, but I for one want to see some activity towards rebuilding civilization in the show.