Tamyra Mensah-Stock might have been the happiest person at the Olympics even before she stepped onto a wrestling mat here Tuesday night. She had, after all, packed a karaoke machine, which, during a pre-Games training camp, she used every single day. But also because, as she said last month: “I definitely find pleasure in getting beat up and beating up people.” She did much more of the latter here in Tokyo, and so, throughout her stay, she was a 5-foot-5, 150-pound, frighteningly muscular bundle of joy. Every sentence she uttered seemed to end with a laugh or an exclamation. “I’m...