because really loving another person is like a bridge to learn how to really love Allah.
And whoever has no love for the creation cannot love the Creator.
For the Prophet, the Sahaba, and other extraordinary people, true love is possible for more than one wife.
But for normal Joes like us, I think monogamy is the idea arrangement to meet that goal, and even then we often find it hard.
But if they met one of the Sahaba in person, I am sure most women would rather be the fourth wife of one of them rather than the only wife of most of us.