Well if you’re comparing 333 Commerce St building (topped out in 1993) with Barad-dûr, as depicted in Peter Hackson’s “The Lord of the Rings” trilogy (released in 2001-2093), then you maybe should ask why Peter Jackson’s art inspiration (specifically illustrator Alan Lee) based their depiction of Sauron’s tower in the AT&T building (although maybe the architect of the building in Nashville did also draw their inspiration from Alan Lee’s art).

I could find no other depiction of Barad-dûr prior to Jackson’s which had that same forked design, most artists drew a sinister-looking but traditionally spired tower design, with the eye peering through a window to some effect.

Tolkien’s book describes the tower like this:

“Then at last his gaze was held: wall upon wall, battlement upon battlement, black tower of adamant, he saw it: Barad-dûr, Fortress of Sauron. All hope left him… …and then he saw, rising black, blacker and darker than the vast shades amid which it stood, the cruel pinnacles and iron crown of the topmost tower of Barad-dûr. One moment only it stared out, but as from some great window immeasurably high there stabbed northward a flame of red, the flicker of a piercing Eye”

No mention of the two-prong fork design that I could find.