Nazi zombies obsession?

I've become obcessed with all of the Nazi zombies made by call of duty. I became obcessed with learning about what happed, and what made the zombies and why the millitary is in the three zombie maps. I heard the secret radio message on Shi no numa. And my theory is that the dead paratrooper or dempyse is related to one of the troopers in the aslyum. So if any one has any theories about the Nazi zombies and the song " luabie for a dead man" means