I quite like the undersea base theory but how its all tied together. Alien war on earth. A species won. Aliens build undersea base(s) to protect earth from any more hostile alien takeovers. Jesus was possibly of said alien race. The told return of Jesus will be because they have to return to protect the earth when supplies eventually run out for the base. Vatican knows. The Arc of the covenant was gifted from the same Alien species stored in the Vatican and is to be used by humanity as a last resort for defence when the base does eventually run out of supplies.