In addition to God needing believing babies, the early saint's apparently needed learn some shit the hard way.
Church leaders taught that participants in plural marriages should seek to develop a generous spirit of unselfishness and the pure love of Christ for everyone involved. (See here.)
Why was polygamy the preferred didactic method for teaching "the pure love of Christ"? I have no clue. Back in Jesus' day his approach was telling people to give all they had to the poor and not judging and stuff like that. The Church seems to be suggesting that God doesn't really care or want us to understand his motives.
Like the participants, we “see through a glass, darkly” and are asked to walk by faith. (See here.)
The only real important thing is that we believe God will give us something for our efforts:
They believed it was a commandment of God at that time and that obedience would bring great blessings to them and their posterity. (See here.)
We view our current polygamous practices the same way.
[T]he Church permits a man whose wife has died to be sealed to another woman when he remarries. Moreover, members are permitted to perform ordinances on behalf of deceased men and women who married more than once on earth, sealing them to all of the spouses to whom they were legally married. The precise nature of these relationships in the next life is not known, and many family relationships will be sorted out in the life to come. (See here.)
In other words, we don't know what the fuck we're doing or why exactly we're doing it, but we trust it's from God and we trust that he'll sort all this shit out even though it's absolutely absurd. Considering all the sealing combinations we've tried out (and the probability that many of those sealed souls won't even make it to Celestial glory), it's safe to say the tapestry of eternal families we've woven will look something like this:
Keeping sealing, dear Saints, but whatever you do do not stop to consider the idea that Joseph Smith made this all up so he could take advantage of several women (and girls).