Дварим 21:15 Комментарий: Chizkuni, Da'at Zekenim, Ibn Ezra & Sforno

כי תהיינה לאיש שתי נשים, “If a man has two wives;” this paragraph is appropriate here as we have just read of a union that is unsatisfactory to the husband, although it had commenced with mutual fondness of the parties. (verses 11 and 14)

When a man has. Thus [these] portions [of marriage to a captured maiden, of the loved/unloved son, and of the rebellious son] are connected to to teach that “a sin causes [one to commit] another sin,” that by taking the beautiful [captured maiden], he would have two wives and they would fight within the household and hate one another. And what is written afterwards [are the laws concerning] a man’s rebellious ad wayward son, and thus we find in the case of David who took [Maacah] the daughter of Talmi, the King of Gashur, at the end of their battle, and [together] they bore [a son] Absalom, who [as it would turn out] tried to kill David and slept with his wives (i.e. concubines), and because of his hand many Israelites were killed.

beloved in his view — not in an absolute sense.