Traditional marriage is between a man and a woman which God (Jesus) had stated. Of course before the great flood there was polygamy but these people had fallen into wickedness and displeased God. Under Noah and his family polygamy was no longer allowed, marriage had become monogamous. Of course the kings of Israel and Judah had fell into paganism and had taken many wives and concubines but of course during these times they were not in favor with God. King David's downfall was because of a woman, and his son King Solomon who was the wisest king his downfall was because of a woman.
And it was not uncommon for a widows spouse to die in which only their male children were allowed to inherit property, but if the widow had no children their brother-in-law was had to marry them and from this union their male child would be the heir of the widow's deceased spouse. This is just how it was back then in any society.
And of course as a victory of war soldiers were permitted to court their women prisoners, but they could not take them as their slaves. The woman prisoner had the right to refuse the soldiers proposal to her.
And the whole rape thing is a misinterpretation of Scripture. If a man were to have relations with another man's daughter this was considered as rape even though she consented. But because of this deception if they were caught the man would have to take her as his wife and pay her father a dowry of 50 shekels and he was not allowed to divorce her. If it was forced by the man upon the woman the punishment for this crime would be death.

