I don't know who you are addressing??
Personally, I see a muti-faceted purpose in God creating Theocratic Israel. Just a few of them are:
1. To reveal the sinfulness of sin and even increase sin so that fallen man must rely upon God alone for redemption.
2. To demonstrate that peace, blessedness, joy, etc. are impossible this side of the eschaton where God will "burn off" the visible earth and create the "New Earth".
3. To demonstrate that the visible Church, of which Israel was the forerunner, was not intended to be permanent nor pure.
4. Salvation comes only through the perfect keeping of the law OR by grace through faith in the incarnate Son of God who would accomplish which no man could, nor can nor ever will.
5. To reveal the coming Messiah according to God's perfect sovereign counsel and providence.