In choosing Abraham, God blessed Abraham’s descendants. So, the Jews were the chosen people because of the faith of their forefathers in the Old Testament, proving that God keeps His word to His people. And from this covenant, Jesus came to us:
Matthew 1:17 Thus the total number of generations from Abraham to David is fourteen generations; from David to the Babylonian exile, fourteen generations; from the Babylonian exile to the Messiah, fourteen generations.
Now, when Jesus was born, the Jews were logistically in the perfect place and the perfect time to receive Jesus into their midst.
Through years of being in captivity and having their populations in servitude to others, their focus was exclusivity and keeping separate from what would contaminate their society. The most faithful Jews constantly focused on their understanding of their relationship to God. Everything in Jewish society until this point has been in keeping pure and holy for the Lord.
The Encyclopedia Judaica provides a secular, historical explanation of this belief, stating that “It would seem that the more extreme, and exclusive, interpretations of the doctrine of election, among Jewish thinkers, were partly the result of reaction to oppression by the non-Jewish world. The more the Jew was forced to close in on himself, to withdraw into the imposed confines of the ghetto, the more he tended to emphasize Israel’s difference from the cruel gentile without. Only thus did his suffering become intelligible and bearable…When the Jew was eventually allowed to find his place in a gentile world, the less exclusivist aspect of the doctrine reasserted itself.” (from Wiki)
The Romans’ hold on Jerusalem was perfect timing for Jesus to be sent. God could use the Roman empire, the known “center of the world,” for His word to be disseminated throughout the Gentile world. In this way, God used the Jews as His refined people into which Jesus should be born, and the Roman Empire to spread His message.
John the Baptist foretold that God would extend His love further than the Jews, saying that being children of Abraham was no guarantee for salvation:
Luke 3:6 and all flesh shall see the salvation of God.
Luke 3:8 Produce good fruits as evidence of your repentance; and do not begin to say to yourselves, ‘We have Abraham as our father,’ for I tell you, God can raise up children to Abraham from these stones.
Then in Galatians 3:7-9 Paul says,
Realize then that it is those who have faith who are children of Abraham. Scripture, which saw in advance that God would justify the Gentiles by faith, foretold the good news to Abraham, saying, “Through you shall all the nations be blessed.” Consequently, those who have faith are blessed along with Abraham who had faith.
And clarifies in verse 14:
That the blessing of Abraham might come on the Gentiles through Jesus Christ; that we might receive the promise of the Spirit through faith.
and sums it up in verses 23-29:
Before faith came, we were held in custody under law, confined for the faith that was to be revealed. Consequently, the law was our disciplinarian for Christ, that we might be justified by faith. But now that faith has come, we are no longer under a disciplinarian. For through faith you are all children of God in Christ Jesus.
For all of you who were baptized into Christ have clothed yourselves with Christ. There is neither Jew nor Greek, there is neither slave nor free person, there is not male and female; for you are all one in Christ Jesus. And if you belong to Christ, then you are Abraham’s descendant, heirs according to the promise.
So, the Jews were chosen because of God’s promise to Abraham, their willingness to be a people seperate unto God alone, and their being in the right place/right time to send the seeds of faith through the Romans. In this way, the fulfillment of the Redeemer is offer to all people through the Jews.