Circumcision is a form of physical distinction that separates one group from others. Circumcision is not a "later" development, it is integral to the root of the story.
4 “As for me, this is my covenant with you: You shall be the ancestor of a multitude of nations. 5 No longer shall your name be Abram, but your name shall be Abraham, for I have made you the ancestor of a multitude of nations. 6 I will make you exceedingly fruitful, and I will make nations of you, and kings shall come from you.
It seems to me that whoever wrote this at least already knew the material from the book of Kings. They at least already knew the story of the Israelite kingdoms. Did they also already know of the success of the Hasmonaeans?
All of the evidence indicates that as of at lest the middle of the Persian era, "Jews" were fairly happily getting along within the Persian empire. They were not exclusive worshipers of YHWH, they were not xenophobic, they integrated with other cultures, they accepted Persian rule, they were getting on with their lives.
What purpose would the stories of the Pentateuch serve?
The stories are clearly very nationalistic. They implore the follower to isolate themselves from those of other cultures, to reject other gods, to mark themselves as different, to obey a different set of laws than those of other nations, the engage in unique dietary restrictions. They call to nationalistic pride and the glory days of military domination. None of this is conducive to living in harmony within a empire dominated by another culture.
Why would a priesthood even set forth these stories in an environment where they could only lead to strife and problems?
These types of writings in ancient times were seldom what they claimed to be. They were also seldom truly historical accounts and more often aspirational. Why would Jewish priests operating within the confines of the Persian state be producing such works?
Look at the boundaries of Israel according to Numbers and the Hasmonean kingdom. It seems to me that either these boundaries were produced shortly prior to the Maccabean revolt, or shortly after it, laying out the aspirational goals of the Hasmonean leaders.