The OT enabled it (see Abraham, David or Solomon.) The NT discouraged polygamy due to an influx of Roman influence in occupied Israel, and the Romans were monogamous. Paul preached that “when a man and a woman are brought together let no man separate”, introducing an entirely new idea to the Jews, and this notion didn’t come from God but from syncretism – it was Christianity absorbing Roman culture. And Roman culture led to traditional marriage predominating.
-But what about now? Would society fall apart if traditional marriage were not the norm?
I see whether to enable polygamy as a cultural decision. There is evidence primates are polygamous, and that humans had polygamous tendencies. Most of the ancient world certainly enabled it. Inuit Indians share their wives with travelers, and Middle-Eastern/Chinese leaders had multiple wives. (Today concubines are replaced with mistresses, but little has changed.)