After disassociating from the WTS I began associating with Evangelical Christians. I was still very much a student of the Bible and even through all of my studies I never heard or read anything that answered that question adequately.
For the most part it appears to be a matter of faith. My question was why would God wait until the first century of our common era to send the Messiah? Why not send the messiah shortly after Adam & Eve (if indeed they existed) "sinned"?
The Watchtower, of course, teaches that this allowed a time for people to show who's side of the issue of universal sovereignty they were on. Sounds good, but it is speculative and can only be "proven" by proof-texting the Bible.
If you read information written by persons who are Jewish (probably the more conservative or orthodox groups) who have responded to the claims of Jesus being the messiah, you'll find that the OT appears to indicate that forgiveness can be given by God without blood, or sacrifice.
These are just some quick thoughts. It will be interesting to hear other viewpoints and learn a bit more. It's a facinating subject.
"The mind, once expanded to the dimensions of larger ideas, never returns to its original size." --- Oliver Wendell Holmes