Did Israel know who Jesus was when He came?
Israel could have known and should have known who Jesus was when He came, but the answer is that Israel did not know. Although they had the opportunity and responsibility to recognize Him, they failed to do so.
Les explains that Paul returns to Israel's situation in verse 18. He reminds his classes in Oklahoma that when Jesus came to the nation of Israel, they could have known who He was and should have known who He was. Yet despite that, Israel did not know. This follows Paul's questions: "Have they not heard? Yes verily, their sound went into all the earth, and their words unto the ends of the world. I say then, did not Israel know?" The context indicates that although the opportunity was there, the nation did not recognize Him.
But I say, Did not Israel know? First Moses saith, I will provoke you to jealousy by them that are no people, and by a foolish nation I will anger you.