In all fairness, with a few notable exceptions, leaders who marry many women do so not because of sex or procreation, but for “political” reasons. That is, by “marrying” the daughter of some powerful clan or faction, it creates a tie with that faction.
The assumption is that through that daughter, they will have a “direct line to the throne”. And to some extent, this is correct.
Marriages also work as informal peace treaties and alliances. It also means that the “first wife”, not necessarily numerically, is like the “chief of staff” of the other wives, and her sons are the heir apparents.
And yes, there is *lots* of contention between wives over their pecking order. Among the Mormons, either Smith or Young set forth very strong rules that wives had to be treated equally. This was almost certainly done to keep the peace.
Harriet Amelia Folsom?