Well to be fair D&D isn't known for the consistency or the structured background (that's one of the reason a miriad of rpg followed this one).
Said that.
My point of view: something strange is happening in Faerun, not only mindfliers are making a move, but there are hidden players able to bring very different races to cooperate (Drows, Bugbears, Trolls, Goblins), furthermore said players were able to made Drows and Goblins to left their faith and embrace the Absolute, the tadpoles this fellas concocted is able to resist the powers of a hag, a high druid, a mindiflyer, it allows a lower vampire to walk under the sunlight, and even death doesn't affect its parasitic tie with character and companions.
Moreover, if my memory doesn't betray me, the Undeerdark too, in this set, is somehow immersed in a chaos of sort.
The circumstances of the area are so weird they attracted the attention of an explorer like Volo.
So I don't find strange that there are minotaurus, I won't be surprised if some enemies that are in act 1 (hag and minotaurs) are being placed there (by manipulating them from the shadows, or by force what could be happened to the minotaurus) to test the recilience, resistence, of the particular strain of tadpoles that infests the protagonists).
