God has committed a significant fraction of Scripture to chronicling families and nations that are generally opposed to Him. Cain's lineage, Ham's & Japheth's lineages, Ishmael's lineage and (here) Esau's lineage are only brief and relatively concise versions of such accounts. Considerable segments of certain books in the Bible (like Exodus, Joshua, Judges, Ruth & Isaiah) give more detailed descriptions of the heathen nations whose paths crossed with God's people. Other books (like Esther, Daniel, Jonah and Nahum) are predominantly about Gentile peoples with Jews playing more of a supporting role in those stories. Even the book of Revelation includes large selections devoted almost entirely to God's interaction with His human enemies. To me, Romans 9:22 is the passage that most vividly explains the reason behind this phenomenon, “What if God, willing to show His wrath, and to make His power known, endured with much longsuffering the vessels of wrath fitted to destruction?" These peoples who stand outside of God's family are still part of the race that God has created for His own glory... and He will receive glory from their existence... whether by demonstrating His patience or His justice; or both, each in its time.
Now, on to the passage: just like Abraham and Lot before them, Israel and Esau outgrew their territory (Genesis 13:6 & 36:7). Sometime after these twin brothers buried their father, Esau was squeezed out of the "Promise Land" picture. We have no reason to think it was a result of ill intentions in Israel's heart, but it came to pass nonetheless. Esau, his three wives, his five sons, his daughters and the rest of his household took all of their things and moved away "from the face" of Israel (Genesis 36:6).
They went to Seir (south of the Dead Sea in modern day Jordan, northwest of Saudi Arabia) where the family grew until it became a whole nation: the Edomites (Genesis 36:9). In their new country Edom multiplied and was filled with men who became dukes and kings in their land. Here is the list of Edomite monarchs: Bela (king in Dinhabah), Jobab, Husham, Hadad, Samlah, Saul, Baalhanan & Hadar (king in Pau). Notice that Moses took the time to specifically point out (in Genesis 36:31) that Esau's descendants were ruled by human kings long before the descendants of Israel were.