How did God respond when Israel missed their calling to reach the Gentiles?

God did not reject Israel completely. Though Israel missed its calling, salvation came to the Gentiles through their fall. God raised up Saul of Tarsus, saved him by grace on the road to Damascus, and sent him far hence as the apostle to the Gentiles, while not casting Israel away forever.

Les explains that Israel stumbled over their Messiah, but God forbade that they should completely fall. Through their fall, salvation came to the Gentiles, though under a different format than Israel’s original calling. In the Old Testament, every Jew could be a priest to bring Gentiles to Jehovah, but they missed it. God did not stop; instead of using the whole nation, He raised up one Jew, Saul of Tarsus, a renegade zealous for the law, and saved him by grace on the road to Damascus. The first thing God let Saul know was that He would send him far hence to the Gentiles. Saul would also go to the Jew, but he was primarily the apostle of the Gentiles. God dispersed Israel, took away their temple and country, but He is not through with His covenant people; they are back in the land awaiting their temple once again.

Acts 9:1

And Saul, yet breathing out threatenings and slaughter against the disciples of the Lord, went unto the high priest,

See the rest

Whom did God raise up after Israel missed their calling to reach the Gentiles?

After Israel's failure, God raised up Saul of Tarsus, a zealous Jew saved by grace on the Damascus road. He sent Saul far hence to the Gentiles, making him primarily the apostle of the Gentiles, though Saul would also go to the Jew.