Two things. Thanks to advancements in medicine people have died and came back from the other side. Some have had horrific stories, others have had utopia stories. My personal belief (emphasis on personal) is that religious indoctrination swayed their ideas.
Secondly African ancestors (the oldest people on the planet and the progenitors of spirituality) have created civilizations based upon the spiritual belief that we do not die in the spiritual form and go on to live eternal. Some even have said that we come back to experience life again. None of them have ever spoken of a westernized version of hell. Fire and brim stone. The closest you can get to that would be the Kemetic spiritual system and even they do not speak of fire and brim stone. Only the destruction of the wicked part of the soul.