Polygamous relationships have been, off and on, the norm throughout most of the cultures of the world through history. The practice was prevalent in the Roman Empire, which even led Paul to tell Timothy that a bishop should have but one wife. Why? Because polygamy was so prevalent in the pagan world.
We are seeing a resurgence of these trends because we are seeing a resurgence of paganism due, in large part, to a feckless church that is failing to reach the broader society with the truth and power of the gospel.
False. Polygamy was practically unknown in the Roman world (adultery was not necessarily uncommon, however). By NT times, it was unknown in the Jewish world as well, and it was never permitted among Christians.
"Husband of one wife" means that Paul is ruling out men who were married and divorced as pagans.