He slipped in his house and broke his jaw. During recovery & physical therapy, his masseter muscle morphed into what his lower jawline looks like now. (I googled it because i said he probably had plastic surgery... and everybody does say his new look is from the slip/fall)
WikipediaIn anatomy, the masseter is one of the muscles of mastication. Found only in mammals, it is particularly powerful in herbivores to facilitate chewing of plant matter. The most obvious muscle of mastication is the masseter muscle, since it is the most superficial and one of the strongest. Structure...
https://en.wikipedia.org/wiki/Masseter_muscle