From what I've read in a comment on another site, in Yuusha ga Shinda the thing that is translated as the "soul" = life energy that anchors the spirit to the body. You see, I've been at a loss what it meant that Shion's spirit was staying without his soul but apparently, it's just that in Yuusha "spirit" is what we normally call soul.
Also, Gods feel so easy-going. Want to possess a human's body to bring darkness to the world? Nah, a bit tired after trying to catch a naked dude, it's easier to call him a god and let him cover his crotch with your head. Get all genocided by demons and necromancers? No problem, let's just make another world for our spirits.
Also, that villainous pervert Isaac is still a cool guy.