Q. Why do you suppose Moses spent 40 years in Midian? What did he accomplish there?
A. There are two reasons why Moses spent 40 years in Midian. One is that he was a fugitive from justice, having killed an Egyptian soldier. (Exodus 2:11-12) And the other is that he was too well known as an authority figure in Egyptian society, being the son of Pharaoh’s daughter, to be of any use to God.
Once everyone who had ever known Moses had died and he was just an old man no one knew, then God could use him to do mighty works on His behalf. (Exodus 4:19)
This principle was explained by Paul in 1 Cor. 1:27-29. “God chose the weak things of the world to shame the strong. He chose the lowly things of this world and the despised things—and the things that are not—to nullify the things that are, so that no one may boast before him.”
When Moses was no longer the powerful son of Pharaoh’s daughter, but a helpless old shepherd from Midian, then he was ready to do God’s work.