Why didn't God's dealings with Israel apply to Gentiles?

Paul writes in Ephesians 2:11-12 that Gentiles should remember that in time past they were Gentiles in the flesh, called uncircumcision by those called the circumcision. He says that at that time they were without Christ, aliens from the commonwealth of Israel, strangers from the covenants of promise, and without God in the world. The teaching explains that while God was dealing with the Jew under the Law—the roughly 2,000 years from Abraham until Paul—everything God was doing for the Jew did not apply to the Gentile because Gentiles were not citizens of Israel. The covenants had been given to the Jew, first to Abraham, repeated to Isaac and Jacob, and Gentiles had no part of them. This is why Gentiles were outside the covenant promises and steeped in paganism, as seen in the ancient temples of Greece, Ephesus, and Corinth.