Luther condemned the practice of taking more than one wife when he said, “…if anyone thereafter should practice bigamy, let the Devil give him a bath in the abyss of hell.”?
St. Augustine doesn’t condemn polygamy. In fact he suggests it was a better way: " who reads with careful attention what use they made of their wives, at a time when also it was allowed one man to have several, whom he had with more chastity, than any now has his one wife," - The Good of Marriage 15
So, while Luther obviously allowed for dispensation under certain circumstances, St Augustine also acknowledges certain dispensations to take more than one wife.
King Louis XII, who stood now in need of two papal favours. … in order to retain Brittany, it was essential that he should marry his deceased cousin’s widow, Queen Anne. No blame attaches to Alexander for issuing the desired decree annulling the King’s marriage or for granting him a dispensation from the impediment of affinity. The commission of investigation appointed by him established the two fundamental facts that the marriage with Jane was invalid, from lack of consent, and that it never had been consummated.
But Augustine, in The Good of Marriage ch 15 says a marriage doesn’t have to be consummated to be valid.
The bigger picture here is that Alexander dissolved a marriage for political reasons. :tsktsk: