Why is Vatican a state?

[Gawdzilla Sama]

It's the DC of the Catholic Church...it's its own entity.

The District of Columbia was created to prevent any one state from "owning" the US capital. This suspiciousness and jealousy went as far as the military, where the Secretaries had to report each year where new officers came from (state), where they were born (if not in the US), who sponsored them for an officer's slot, etc.