User blog comment:Nightband/Season Seven Plot Hole?/@comment-10603955-20121214011240/@comment-10603955-20121216200805

Remember, in a fictional universe. Anything could've happened.

God might not have been "God" at the time, in the Supernatural universe, when he made the Leviathan. Instead, perhaps he was a bit weaker at the time; younger maybe, and went by a different name back then, which later he had a character developement and became God.

We don't know. It's fiction, anything could've been going on back then.