The problem with polygamy is it's usually a sexist arrangement.
Even going back to biblical days it was written that King Solomon had 700 wives and 300 concubines. Can you imagine a queen having 700 husbands and 300 boy toys? Probably not.
Then again (men) wrote the bible!
All of us to some extent are brainwashed by the culture we are born and raised in. I supposed if one grew up where polygamy was commonly practiced they'd have no issues with it.
Being "in love" with someone usually brings a form of possessiveness where one does not want to share their mate intimately with others.
There is no way I could truly be "in love' with a woman and yet find it okay for her to please and be pleased by other men.
I suspect women feel the same way. If a woman gives her man the "green light" to take on another wife it's more than likely the result of her emotionally taking a step back from him. She may even be relieved to not have to shoulder the burden alone. This would be especially true if she's no longer "in love" with him.
When someone is "in love" they want their mate all to them self!