The author's examples remind me of the words of Jesus, "For your hardness of heart, Moses allowed you to divorce your wives." Some commentators understand this to mean that, without the provision for divorce, men would just kill a wife who was incapacitated or otherwise unsatisfactory, so as to be able to marry another. This possibility is implied in the author's claim that polygamy is a solution to the "problem" of a wife who is mentally incapacitated and can't agree to divorce: it's a good thing the man can take a second wife legally, or he'd have to kill the first one.
Hardness of heart is also behind the example of the rabbi who married hundreds of women and provided them with food. There was a famine, the author says ... but obviously there was enough food, or the rabbi wouldn't have it for his wives. The problem was hardness of heart when it came to distribution ... and apparently nobody was willing to help a starving woman unless he got to use her for sex.
As I understood the story, they could not eat of the priest’s allotments unless they were in his family and marriage accomplished that, so that he “saved” 300 women.