The old wife explanation (which I do not subscribe to) is testicle damage. Next is genetic and last is damage to the antler bud. My wife and I took pictures of this elk Monday at our cabin in interior BC.
I know from experience that damage to a horn bud or insufficient de-horning techniques in goats and cattle will result in the regrowth of a deformed horn. Makes some sense that a damaged antler bud might develop odd shaped antlers as well.
This is just a guess, and probably a bad one; as horns and antlers are very different structures.
This deer was just killed in Tennessee. Possible world record non-typical, and according to the article only 3 years old.
Johnson City Press:
Possible world record deer killed in Tennessee