Could be the bronchitis but Mariah Carey's vocals were sounding very strained and tired last night.
She will always be the people's legendary diva but let's be honest, she used to hit notes so effortlessly. She did find strength to hit that last note, although I'm not convinced it was completely live. During that last note, editing showed the camera panning out to a wide shot where you could barely see her. Not terrible, but she's had better days.
Alternative: