Here you have switched to a completely different meaning of peace! Whatever the Japanese are doing to themselves in their homes does not harm another person outside of it so that is what’s being measured as peaceful. Another issue is the lack or reporting in developing countries. I am very sure of the records we do have of suicides in japan, but do we really know the number of suicides that actually happen in countries like Pakistan and Afghanistan? No, we don’t. They are not accounted for. Developed countries hold a better record of these events, that’s all.
Now as to why I think religion plays a role in keeping peace or destroying it, I believe the lack of religion is just one less thing to worry about for people. It cuts down many crimes simply because people don’t really care about religions in the least religious countries of the world. Again, there is no denying that the least religious countries have the least number of crimes even on the state level where country governments don’t play a big role. Religion clearly causes a great divide in people, which even on local level raises the crime rate.