In Genesis 27:1–40, why did God permit Jacob to trick Esau out of his birthright?
In a patriarchal society, Jacob, as the younger twin brother, was always expected to defer to Esau. This story is told partly to challenge the idea that God acts exactly like any patriarch. The stories of Cain and Abel, of Leah and Rachel, and of Joseph as being favored over his 10 older brothers all make the same point.
The story of Jacob and Esau stresses their common origin but also the divergent paths of their descendants. The 12 sons of Jacob give rise to the people with whom God makes a covenant at Mt. Sinai. The descendants of Esau eventually become pagans—though still loved by God.
Your question suggests that Isaac, Rebecca, Jacob, and Esau were simply actors following a script written by God. That’s an easy assumption because humans necessarily live in past, present, and future. God, however, lives in the eternal now, not bound by time as people created by God are.
The experience of separation within the human family comes first; the explanation for that separation comes later—as the story of how Jacob stole Esau’s birthright demonstrates. Human freedom remains both real and important to God.