Speaking of all those people that have come and gone, why is it that man's "deliverance" didn't happen earlier?
If I understand your question correctly, you're asking, "Why, through several millenia of human history, did Christ come to earth only 2,000 years ago?"
It could quite easily be argued that history had to be "ripe" enough to ensure Christianity became available to all of humanity. If you look at the belief systems that grew up prior to the time of Christ (i.e. Hinduism, Buddhism, various animist/pagan religions, etc.) they have either died out, or remain relegated to very specific regions. Only the infrastructure and communications of the Roman Empire could ensure the spread and widespread institutionalization of the very same Christianity it sought to snuff out at the beginning. Christianity not only extinguished the gods of Rome, but served as the foundation of western civilization that would ultimately spread it around the world and make it accessible to all.
So the question, "Why didn't Christ and Christianity appear earlier?" is probably best answered simply by saying that It couldn't have, and still be what It is. Having said that, there were any number of prophets to let everybody know It was coming :-)
Who really knows if it has yet? For yourself, it just depends on what you believe.