Should Israel have known who Jesus was from the Old Testament?
Yes, the Old Testament was full of Him, so Israel could have known who Jesus was from it if they had simply studied it. But they did not know; as Paul says, had they known, they would not have crucified Him.
Les teaches that Israel should have known who Jesus was because the Old Testament was full of Him; they could have known if they had simply studied it, but they did not. He points out that the princes of this world did not know, for had they known Him they would not have crucified Him. Les also compares Israel's ignorance to America, which has the Gospel and Bibles everywhere yet few understand biblical prophecy or that the Lord is about to intervene in human history.