Why Did Jesus focus His Ministry on Jews and not Gentiles?

We see in Matthew 10:5-6 that Jesus sent his 12 disciples specifically not to Gentiles and Samaritans, but to Jews. In Matthew 15:22-28, Jesus tells a Canaanite woman asking for help that He was only sent to the Jews.

God chose to establish Himself through Abraham and his descendants, the nation of Israel (Genesis 12:2-3). And, through this lineage, Jesus would be born. So, Jews were not only the chosen people, but also a blessing to all people as the lineage from which the Messiah would come.

God in the Old Testament pointed to Jesus through many prophesies. Jesus was the fulfillment of all of history as the Savior of mankind.

When Jesus came, His primary purpose was to die for sins, but He also needed to start establishing His church. This was the primary purpose for the 12 apostles - they would spend 3 years with Jesus to learn from Him, to be discipled by Him.

So, looking at this together, it appears the reasons why Jesus preached primarily to the Jews only were:

1. Jesus was the fulfillment of the promises of the Old Testament, given primarily to Jews.
   
2. God through history had focused His message through the Jews.
   
3. The Jews were the ones knowledgeable in the Old Testament and what God had done to prepare for Jesus, so they would be the best ones to take His message out to the world.
   
4. God was preparing to bring His message to all mankind (Luke 24:47, Acts 1:8), but God needed to first establish a foundation. The focus on Jews was to build a stable foundation before it was taken to the Gentiles.
   
5. Notice this foundation was really the 12 apostles, not Jews in general. Jesus preaching really was focused on the 12 apostles.

To summarize, God worked through the nation of Israel, and this was the foundation for His church. Jesus' purpose, in addition to dying for sins, was to establish His church through His apostles. After His death they freely took His message to all nations and peoples (as seen in Acts 2). But Jesus made it clear that, even though His focus during his ministry were Jews, Gentiles were also welcome and fully accepted with Him in heaven.

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Matthew 10:5-6 — These twelve Jesus sent out after instructing them: "Do not go in {the} way of {the} Gentiles, and do not enter {any} city of the Samaritans;
but rather go to the lost sheep of the house of Israel.

Matthew 15:22-25 — And a Canaanite woman from that region came out and {began} to cry out, saying, "Have mercy on me, Lord, Son of David; my daughter is cruelly demon-possessed."
But He did not answer her a word. And His disciples came and implored Him, saying, "Send her away, because she keeps shouting at us."
But He answered and said, "I was sent only to the lost sheep of the house of Israel."
But she came and {began} to bow down before Him, saying, "Lord, help me!"

Matthew 15:26-28 — And He answered and said, "It is not good to take the children's bread and throw it to the dogs."
But she said, "Yes, Lord; but even the dogs feed on the crumbs which fall from their masters' table."
Then Jesus said to her, "O woman, your faith is great; it shall be done for you as you wish." And her daughter was healed at once.

Genesis 12:2-3 — And I will make you a great nation, And I will bless you, And make your name great; And so you shall be a blessing;
And I will bless those who bless you, And the one who curses you I will curse. And in you all the families of the earth will be blessed."

Luke 24:47 — and that repentance for forgiveness of sins would be proclaimed in His name to all the nations, beginning from Jerusalem.

Acts 1:8 — but you will receive power when the Holy Spirit has come upon you; and you shall be My witnesses both in Jerusalem, and in all Judea and Samaria, and even to the remotest part of the earth."

Acts 2:10 — Phrygia and Pamphylia, Egypt and the districts of Libya around Cyrene, and visitors from Rome, both Jews and (I.e. Gentile converts to Judaism) proselytes,

Galatians 3:16 — Now the promises were spoken to Abraham and to his seed. He does not say, "And to seeds," as {referring} to many, but {rather} to one, "And to your seed," that is, Christ.

Galatians 3:29 — And if you belong to Christ, then you are Abraham's descendants, heirs according to promise.

Acts 13:46-47 — Paul and Barnabas spoke out boldly and said, "It was necessary that the word of God be spoken to you first; since you repudiate it and judge yourselves unworthy of eternal life, behold, we are turning to the Gentiles.
~"For so the Lord has commanded us, `I HAVE PLACED YOU AS A LIGHT FOR THE GENTILES, THAT YOU MAY BRING SALVATION TO THE END OF THE EARTH."'

Acts 18:6 — But when they resisted and blasphemed, he shook out his garments and said to them, "Your blood {be} on your own heads! I am clean. From now on I will go to the Gentiles."

Romans 10:12 — For there is no distinction between Jew and Greek; for the same {Lord} is Lord of all, abounding in riches for all who call on Him;

Romans 15:16 — to be a minister of Christ Jesus to the Gentiles, ministering as a priest the gospel of God, so that {my} offering of the Gentiles may become acceptable, sanctified by the Holy Spirit.

Isaiah 42:6 — "I am the LORD, I have called You in righteousness, I will also hold You by the hand and watch over You, And I will appoint You as a covenant to the people, As a light to the nations,