Well in order to rebuild a system you have to break it first.
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.