If a government accidentally killed millions of people across the globe, how is that not political? Even a diplomat killing someone in a car accident causes a p

If a government accidentally killed millions of people across the globe, how is that not political? Even a diplomat killing someone in a car accident causes a political incident, I don't see how you could remove political repercussions from an accident that kills millions. There's little incentive for a government to admit responsibility and lots of incentive to hide it.