Since we're all throwing some theories around I guess I'll put my
in.
I'm a Christian and I believe that it's true that Satan and his servants are walking around the earth as we speak. My theory is all the religions were inspired by a confusion of sorts. I'll take the Greek religion as an example.
The Bible says that Satan and his servants are always looking for people to take with them when the time of judgement comes. I think Satan and his servants posed or tricked the Greeks about Zeus, Athena, Mercury, ect.
Please take a minute to think about this for a moment. The Greeks were busy worshiping Zeus and didn't worship the Christian God. What happened to the Greeks who worshiped Zeus instead of the Christian God? Well they all fell for Satan's trick and are waiting for him in hell.