וְאֵ֙לֶּה֙ הַמְּלָכִ֔ים אֲשֶׁ֥ר מָלְכ֖וּ בְּאֶ֣רֶץ אֱד֑וֹם לִפְנֵ֥י מְלָךְ־מֶ֖לֶךְ לִבְנֵ֥י יִשְׂרָאֵֽל׃
And these are the kings who reigned in the land of Edom before any king reigned over the children of Yisrael.
Torah Temimah points to Bereishis Rabbah 83:2.
Sefaria · Bereishis Rabbah 83:2
לפני מלך מלך לבני ישראל — מלמד שהיו מלכים באדום קודם שהיו מלכים בישראל.
“Before any king reigned over the children of Yisrael” — this teaches that there were kings in Edom before there were kings in Yisrael.
The Midrash notes the chronological priority of Edomite kingship.
Derash on the historical sequence (Bereishis Rabbah).
Edom had established monarchy before the rise of kingship in Yisrael.