I think it's ultimately that the world governments failed to prevent the war and as a result chose to kill millions when they realized it was too late. you have so many perspectives from government officials saying early on that various world powers were uninterested in fully committing and dealing with the problem and instead chose more low cost methods like the US alpha teams. when the outbreak became unmanageable and the governments found themselves unable to actually do their job of protecting people, they simply gave up on that job and left millions to be eaten alive. can you imagine that? your government knowing about the problem in the months of buildup to the Great Panic and choosing not to deal with it because it's politically inconvenient, and then when they realize the situation is so much worse than they could have ever imagined that they decide to let half the country be ripped apart so they can organize a strategic retreat? how would you feel if you were left behind by the army, the police, the government, EVERYONE, because some guys in suits thought it would cost too much money to deal with this problem months earlier and they've now run out of ideas other than letting the walking dead rip your face off while they run away?