When John the Baptist came saying, Behold the Kingdom of God is at hand, and then Jesus said, Behold the Kingdom of God is at hand, they literally meant the Kingdom of God was being offered to Israel. But it was not meant to be this way.
God through His foreknowledge knew Israel would freely reject Christ. If it would have meant to be that way, there would have been no Church Age, we would have went straight to the Kingdom Age with Christ ruling on this earth.
See, Christ only came to the lost sheep of Israel. They were chosen of God to evangelize the world, introduce the world to Christ that the Gentiles might be saved. But Israel failed miserably and killed their own Messiah.
So God chose the Gentile Church to evangelize the world in place of Israel. Well, 95% Gentile, God has always had a small remnant of Jews.
But Paul tells us that God is not finished with Israel, far from it, he said Israel will yet fulfill their original calling. This is after "all Israel will be saved" as Paul plainly told us.