this definitely wasn't just a lip-synching fail... you can see the improvised runs with NO sound! It clearly was some kind of sound issue.. For the most part she actually did very well if yall watch the other performances..
Mariah earned her right to do whatever the **** she pleases. With 18 number ones, an unprecedented legacy, and being one of the best selling artists of all time - She can improvise, lip sync or hit the odd dead note.. None of that matters. She still sings better than most of the divas half her age - 20 years into her career at that...