Possible explanation of the description of the two brothers:
Legends of the Jews vol. 1, by Louis Ginzberg:
At the end of the years of famine, God appeared unto Isaac, and bade him return to Canaan.
Isaac did as he was commanded, and he settled in Hebron. At this time he sent his younger
son Jacob to the Bet ha-Midrash of Shem and Eber, to study the law of the Lord. Jacob
remained there thirty-two years. As for Esau, he refused to learn, and he remained in the
house of his father. The chase was his only occupation, and as he pursued beasts, so he
pursued men, seeking to capture them with cunning and deceit.
Easton's Bible Dictionary - Birthright
(1.) This word denotes the special privileges and advantages belonging to the first-born son among the Jews. He became the priest of the family. Thus Reuben was the first-born of the patriarchs, and so the priesthood of the tribes belonged to him. That honour was, however, transferred by God from Reuben to Levi (Num 3:12, Num 3:13; Num 8:18).
(2.) The first-born son had allotted to him also a double portion of the paternal inheritance (Deu 21:15-17). Reuben was, because of his undutiful conduct, deprived of his birth-right (Gen 49:4; 1Ch 5:1). Esau transferred his birth-right to Jacob (Gen 25:33).
(3.) The first-born inherited the judicial authority of his father, whatever it might be (2Ch 21:3). By divine appointment, however, David excluded Adonijah in favour of Solomon.
(4.) The Jews attached a sacred importance to the rank of "first-born" and "first-begotten" as applied to the Messiah (Rom 8:29; Col 1:18; Heb 1:4-6). As first-born he has an inheritance superior to his brethren, and is the alone true priest.