It is not a concept that originate with Paul. It was the norm in Jewish society centuries before Paul’s death. Whenever Jesus discussed marriage, divorce, and fidelity, he used singular pronouns in such a way as to indicate that it was simply assumed that each person had no more than one spouse. As for your claim that “there was bitter argument” in the early Christian church about monogamy vs. polygamy, you’re flatly wrong. We’ve no evidence there was any such argument.