Just because events happened in the bible does not mean that God was pleased with them nor ordained them.
The bible is clear about marital fidelity and how marriage is to represent Christ and the church. The book of Genesis even states that man (singular) shall leave his family and cleave to his wife (singular) and they (the two of them) shall be one flesh.
Yes, they were plenty of polygamous relationships in the bible and there are even today.
Jacob had two wives. He loved Rachel because she was beautiful and he hated Leah because she was physically unattractive to him and he was "tricked" by her father into marriage with her......the bible says so. Jacob was a deceiver himself and he met his match with Laban and it made him mad and the bible says he hated Leah for it.
He also had children by women that he wasn't even married to.
Did God just shut his eyes and ignore it? No.
Did God not saying anything to Jacob about it mean that God approved of it all....the deceit, having multiple sexual partners, the hatred of fellow human beings? No.
Mankind has a free will to engage in whatever behavior he chooses. We aren't puppets on strings. We make mistakes and we choose our lifestyles and we must live with all consequences.
Sometimes God blesses his people in spite of their lifestyles. Can I explain why that happens?
No.
But God's will prevails, whether mankind and womankind lines up with his will or not.
God did not bless Jacob and his family because of their lifestyles, but in spite of it.
Does this mean that we can live any old way we want to and expect that God will just bless us anyway?
NO. That's a very sinful act of testing God. Pushing the boundaries and hoping that He won't do anything about it.
Instead, we should live a pleasing life inside the boundaries and hope that His name is glorified in our lives.
Jacob eventually did turn to God in submission. And he honored the wife that he dishonored for all those many years by burying her, when she died, with his parents Isaac/Rebekah and his grandparents Abraham/Sarah. She was the only "wife" thusly honored.
That's the best answer I can give you.