When God brings the good news to someone, He doesn't force it into his or her head directly. He brings it via a messenger, commissioned by Him, who has to put on shoes, fill up the gas tank, and go
someplace where people are willing to listen. Paul was the only guy who got it directly. Since then, it has been a slow but inspired slog. It pleases God to do it this way so that the heralds might be able to suffer and then later to enjoy a better resurrection.