I thought that 'sightings' of Elvis, and even photos of him after death, demonstrate popular credulity about life after death. I suppose you could say that some people don't want Elvis to be dead, or maybe they have some other reason, to wish him alive.
Doesn't this offer some insight into how such legends arise? We also know that many people, after bereavement, have very strong experiences of their loved one still being around, part of mourning I guess.