[dukeleto]

Man, really don't you have any impression about "Walking Dead"(including comics and tv-show)?
On Walking Dead the main reason is never told.
On Walking Dead it never shows how society as it falls.
On Walking Dead there is no "in fact", "essentially", "originally" etc...
On Walking Dead, people lives and dies and that's all, there is no turning back.
It tells us stories -good stories- about situations. We see characters whose actions are important much more than the reasons. Something happens- it just happens, and that's all. I strongly advise you to keep your expectations with this direction.
In my opinion, there is no turning back and I'd love to see as it is not turning back.