The problem is the Bible itself says Israel was grafted into the tree and if the tree is Israel grafting itself into its own self is illogical and cutting off a branch called Israel when the whole tree is Israel is also illogical too.
You obviously don't understand God's concept of 'Israel'. It's not just about a little ole nation in the middle east filled with Jews. The name Israel is the Salvation name under Christ Jesus. So it's a lot more than just a certain people. It's about God's future Kingdom under His Son, our King of kings, and Lord of lords.
It all began with God's Birthright first given through Abraham.
1. God first gave the Promise by Faith (The Gospel) to Abraham; Abraham believed and God counted to him as righteousness. This is the same Faith we have believed, which is Paul called believers the children of Abraham in Galatians.
2. Other Promises were included to Abraham, a great number of seed, ruling the gates of thy enemies, plenty of corn and wine.
3. God's Birthright then passed to Abraham's son Isaac.
4. The Birthright then passed to Isaac's son Jacob.
5. Jacob wrestled with The Angel of The Lord and prevailed, and demanded a blessing. The Angel gave Jacob a new name, Israel, which means 'to prevail with God's help', i.e., to overcome.
6. The name ISRAEL became the Birthright name from God to represent God's Salvation Promises especially in The Gospel of Jesus Christ which they were to have care of for all nations. God told Jacob "a nation" and "a company of nations" would be of his seed.
7. The Birthright then went to Jacob's son Joseph, who was separated from his brethren in Egypt.
8. Joseph was exalted in Egypt, and had two sons, Manasseh and Ephraim.
9. Jacob blessed Joseph's two sons and said Ephraim would become "a multitude of nations", and Manasseh would also become great.
10. God's Birthright blessing then went to Ephraim and Manasseh, where it still is today.
11. Because Solomon allowed pagan worship in Israel, God split old Israel into two separate kingdoms, a 3 tribe kingdom in the south at Jerusalem under Judah, and a 10 tribe kingdom in the north at Samaria under a king born of Ephraim. The two kingdoms had war against each other.
12. The northern "kingdom of Israel" did pagan gold calf idol worship.
13. God brought the kings of Assyria upon the northern kingdom, and took them captive to Assyria and the lands of the Medes. Only the 3 tribe kingdom of Judah in the south was left in the land.
14. The ten tribes would loose their knowledge of their heritage as part of Israel. They would become as Gentiles, living as Gentiles, and God would scatter them further through the countries.
15. The southern kingdom of Judah would also fall away about 120 years later, and God would bring the king of Babylon, Nebuchadnezzar, upon them, and carry them captive to Babylon for 70 years.
16. After the 70 years, a small remnant of Judah, Benjamin, and Levi would return to Jerusalem and rebuild the temple, city, and walls. The ten tribes remained beyond Euphrates, but still a very large number. The majority of Judah would choose to stay in Babylon after the 70 years, and be further scattered through the countries as Israel (ten tribes) were.
17. The ten tribes of Israel drop out of history. The Jews loose what happened to them. The Jews (southern kingdom of Judah, Benjamin, Levi, some small remnants of the northern tribes, and the strangers) keep their heritage as Israel, and the holy days and sabbaths.
18. The ten tribes scatter west, through the Caucasus mountains, around the Black Sea, and into Asia Minor and Europe. They keep their false Baal idol worship they fell away for. God leads them into the 'wilderness' of new lands in the West. Each area in Asia Minor and Europe they create cultures each with their own name for their ancient Baal worship. God gives them the full strength of their lovers of Baal.
19. When it is time, The Gospel of Jesus Christ is preached to them, and they become the Western Christian nations, the fulfillment of the "company of nations" of Jacob, and the "multitude of nations" of Ephraim. They put away their Baal idols, and receive The Gospel. They are the lost sheep of the house of Israel (ten tribes).
20. Among scattered Israel, Gentiles believe The Gospel also with them, and they both, together, become Christ's Church. Many of the house of Judah scattered from Babylon also believe on Jesus and become part of His Church in the West.
21. The remnant of Judah, Benjamin, and Levi, i.e., the Jews, remain blinded by God to The Gospel, so The Gospel would go to the Gentiles (and to scattered Israel of course!).
This is why when Apostle Paul said "commonwealth of Israel" in Ephesians 2, that's what Christ's Church is, a 'commonwealth' of nations of believers under Christ Jesus. Thus God made use of Israel's rebelliousness in falling to Baal worship.