It has always been God's plan to have those on earth who would represent Him. In fact, this was His purpose for all mankind as He created mankind in His image (Gen 1:27). The two words, "image" and "likeness" used together imply both a static picture as in a photo, and a dynamic image as in a shadow or reflection - in other words, mankind was to both "look" like God (not physically, since God in His essence does not have a body, but spiritually) and act like God (moving as He moved, standing still as He stood still, just like a shadow or reflection would.) He then gave our first parents the mandate to "fill the earth, subdue it and rule over it." (Gen. 1:28) In other words, they were to be His vice regents on earth.
Our first parents fatally damaged their image and likeness of God through sin, not only for themselves but for all their descendants. By their obedience to satan instead of God, they also handed over the rulership of this world to the devil.
However, God still wanted a people to represent Him. (None of this took God by surprise. He knows all things, and knew from before the creation of the world exactly what man would do, so technically it is not right to speak of Him having a "plan B.")
Abraham demonstrated His faithfulness to God through obedience. When God told him to leave his country and his father's household - something that was not normally done in those days - he did. (Genesis 12:1-6) God then made him a promise that He would give the land to Abraham and his descendants (Gen 12:7) Later He confirmed this to Abraham as a covenant (Gen 15). Although Abraham and Sarah tried to make this happen by natural means, by Abraham fathering Ishmael through Sarah's maidservant, God made it clear that His promise would not come through that line, but through a son born to Abraham and Sarah, and in due time this was fulfilled with the birth of Isaac. (Gen 21:1-7)
Fast forward through the days of the Patriarchs to the time when Joseph was sold into slavery in Egypt by his brothers. Remember, this whole family (as obnoxious as some of them were) had the blessing of God because of the covenant of God with Abraham. When, after a series of trials, Joseph ended up as 2IC over all Egypt, Jacob sent his other sons down (not knowing that Joseph is the ruler) to buy grain during the famine. Joseph tested them out a bit, then finally revealed himself and brought them all down to Egypt as honored guests.
Fast forward another 400 years. The Hebrews have now become a large part of the Egyptian population. They have also become slaves. But they are still God's people, because of God's covenant with Abraham. Pharaoh decides they are a problem, and that he needs to drastically cut back their numbers, but as a direct result of his attack Moses ends up being brought up in Pharaoh's palace. (Exodus 1:1 - 2:10) When he grows up, Moses identifies with his own people. He knows that he is called to be their liberator, but tries to do it in his own strength, and as a result ends up spending 40 years at the edge of the desert tending sheep, till he is in a place where God is able to use him. Then God sends him back to bring His people out of Egypt and establish them as a nation in their own right. After they have come out, God tells them, "Now if you obey Me fully and keep My Covenant, then out of all nations you will be My treasured possession. Although the whole world is Mine, you will be for Me a kingdom of priests and a holy nation." (Exodus 19:5-6)
Priests are those who represent God before man, and man before God. So Israel was meant to be God's corporate representative on earth. They were chosen because of God's covenant with Abraham, and confirmed in that position through the Mosaic covenant. Unfortunately, they did not live up to that position. Rather than touching the world with God, as they were supposed to, they saw themselves as special and better than the world, whilst at the same time indulging in all the sins of the nations around them. Nevertheless, God promised that the day would come when He would make a new covenant with them. (Jeremiah 31:31-33)
In due time, God the Son took on humanity and became the Son of God in the person of the Lord Jesus Christ. He not only paid the penalty of sin for all those who would receive Him, but He actually began a new race of people - not a physical race, but a spiritual race: those who would be born not of the flesh, but of the spirit. (John 3:6) That "race" is the Church, the Body of Christ. Through Christ's death, God has made a new covenant with us, by which we become His people and His representatives. (Luke 22:20) Because of God's covenants with Israel, and His promise through Jeremiah, the Jews were the first ones given opportunity to become part of that race. But because this "race" is spiritual rather than physical, it can be extended to all peoples, gentiles as well as Jews.
God's purposes with the physical Jewish race are not over, however, as Paul makes clear in Romans 11.
blessings,
Lynn