It's not like Jesus came and said, "listen, I know you're all desperate for eternal life, so here's what I'm going to do.....".
Infact it was Christ who came and told us about it.
well i'm afraid i have to disagree with you on this, the concept of eternal life is pretty much universal in all religions in some form or another, in fact being one with your god/s having a person grant you eternal life was a pretty common religious theme
norse, celtic, greek, roman, many of the mystery religions believed it
many things were looked on as eternel, so why not the human soul?, it comes down to fear of death being the end