I think the theory was that smiths must have been very valuable memebers of the tribe once metals were discovered, so smashing their legs was a reasonable ruse to stop them running off in search of higher wages elsewhere. But how that applies to kings, or even queens, I am not sure.
Sheba had mines, I suppose, so something to with metallurgy? Might explain the deformed leg, or the hairy leg...descended from devilish/djinn/underground troll type?