Since none of us were there, we can only speculate. One of those speculations I've heard is that it was actually based on a popular story at the time. What is kind of interesting is that it is clearly not talking about eternity since it does not describe either the Jewish, nor the Christian version of eternity. And it doesn't describe the time between the death of the body and the GWTJ in Jewish nor Christian viewpoints.
And it seems to be about the 5 brothers and, key, the "not believing even if someone is raised from the dead". It appears to be Jesus talking to the descendants of Joseph and looking forward to their impending disbelief even after Jesus' resurrection.
And there is no information about the rich man to suggest that he did anything warranting eternal torture. In fact, there is a chart on the site I linked to that demonstrates that the actual actions of the two men do not warrant either of their conditions, unless one would argue that poverty is, at its core, a virtue of some sort, and being rich, at it's core, is a sin. I'm buying neither of those ideas.