We might think of toledoth (an account of the generations) as meaning the story of the offspring of a person, or, in the case of the first toledoth, of the heavens and the earth. So perhaps Moses (the author of Genesis 36) was implying that Esau had two sets of offspring: first, his immediate, personal family, and second, the country he founded and its line of leaders.
While the first toledoth (Gen 36:1-8) covers his wives and sons, the second reiterates these and proceeds immediately to his grandsons, chiefs, and kings of Edom, as well as unrelated Horites. The two broad sections seem to cover, first, Esau’s family offspring and, second, his political offspring. That they have separate focuses in this way is supported by two contrasting facts. The first toledoth concludes with Esau and his fairly small nuclear family relocating to Seir. The second toledoth, by contrast, goes into grandsons, names them as "chiefs" (KJV has "dukes"), and later gives a line of Edomite kings.
The second toledoth is rendered by the NIV, but not by the NASB or many other translations, as poetry. If it is poetry indeed, I cannot account for why.