I’m not trying to make any kind of point but I’m curious. Why do you think it was so crucially important in Jacob and Esau’s generation who got the blessing but didn’t matter a bit in the next? The descendents of all 12 of Jacob’s sons were in God’s covenant but for some reason Esau’s were cut out.
Yishma`'el and `Esav were cut out because they were evil men. The twelve sons of Jacob were all righteous.
That answer won't satisfy you if you're a Calvinist, but it's the traditional Jewish position.