I go with cultural replacements here. Likely ultimately similar
  to what they're all saying. Old religions are dying. Needed
  replacements. Angels become aliens. Devils become aliens. UFO is
  future tech chariot of fire. Alien civilization/planet becomes
  Heaven. Alien apocalypse (as with all apocalypse stories,
  including ones out of Science or wherever) are a rehashing of
  Protestant-era obsession with Revelations apocalypse with new
  demons, new Devil, new Utopian era of peace. In short, same
  story, different characters. We all fall into it because it's a
  part of our cultural heritage. Sometimes the ones that buy into
  the story the most are those who try to reject the original
  because they want THEIR version of the same story to replace it
  completely. So, there ya go. My take :)