The assumption is that Jesus envisioned no delay. Recently the Jesus Seminar concluded that few of the words in the Gospels can be attributed without question to Jesus himself. It is a circular argument. I reject those assumptions. Yes, the Gospel writers shaped the sources they had received in order to emphasize certain elements of Jesus' life.
All historians do the same.
But honest historians use their materials with integrity. If that is the case, your assumptions of what MUST be true or false cloud your evaluation of Jesus. I've chosen in this JesusWalk series to try to get at what Jesus is saying, and let his words speak for themselves. The Pharisees saw the same miracles and heard the same teachings as the multitudes. But because Jesus threatened their belief-system and power structure, they rejected him, and ultimately killed him.