>Jacob had two wives because he understood human nature
Jacob wanted Rachel because she was pretty. But his future father-in-law, Laban, tricked Jacob into marrying Rachel's older sister, Leah, who had weak eyes.
So they came to an agreement that Jacob could have Rachel as well, but then he had to work for Laban for another 7 years.
But Jacob loved Rachel more than Leah.
https://www.biblegateway.com/passage/?search=Genesis%2029&version=NIV