Why was Israel's rejection of the suffering Savior a problem?
The problem was that Israel wanted only the king and kingdom, not the spiritual salvation they also needed. They required remission of sins through God's tender mercy; rejecting the suffering Savior blocked that fulfillment and their role to bring light to the Gentiles.
Les explains that the Old Testament contains two parallel thoughts: the king and the kingdom, and a suffering Savior. Every Jew wanted the king and kingdom but did not want to deal with the Savior, and that was their problem. They were to be saved from physical enemies, have a physical kingdom, peace and prosperity, but they also had to have spiritual salvation—knowledge of salvation by the remission of their sins through the tender mercy of God. Their rejection meant they missed that spiritual salvation. As they would come to spiritual, political, and physical fulfillment, the next step for Israel was to give light to those in darkness and the shadow of death—the Gentiles. Israel was to have the light of the world and take it to the Gentiles. Les then moves to Acts, showing how the Old Testament flows into the New: Messiah came, was rejected, crucified, and ascended.