Why did Jesus have to die on the cross?
Jesus had to die on the cross to fulfill the eternal purposes of God. Although Israel could have received the King and the Kingdom had they believed, God in His foreknowledge knew they would reject Him, so all things fell into place to accomplish His eternal purpose through the cross.
Les explains that the first seven signs in John were directed at Israel before the crucifixion. Early signs showed Israel without joy, sick, and impotent, yet still having a flicker of hope to recognize the Messiah. As Christ appeared to the nation, based on Old Testament promises, they could have had the King and the Kingdom if they had believed Him. But God in His foreknowledge knew they would not accept Him and would reject Him, so everything fell into place to fulfill His eternal purposes, which was the cross. Les says He made a valid offer; they could have had the King, but they refused to see Him. Through those early signs, the nation could have repented, recognized who He was, and experienced the fruition of all the promises. By the account of Lazarus, it was evident they were not going to accept Him, and the cross stood as God's eternal purpose.