She crumbled under pressure like Hillary

That's a huge work out singing the way Carey and Houston sang. I'm sure it takes a toll on you after years of doing so. And if you do not take care proper care of yourself, over time you just won't have it in you anymore. Add ageing and other elements (such as Houston's drug problem), and it's almost impossible to keep up with how you were in your healthier, stronger, younger days.

I don't think she can sing any more. Whitney Houston had the same problem. I have no idea if it's drugs or just the result of an aging Carey but I just don't think she has the pipes to sing at this point. And it's not like she is old. She just seems totally out of it all the time. I got the same impression from Whitney Houston and it turns out she was heavy into some dangerous drugs.
It's a shame because when you go back to her early performances, she had a very strong voice.

Ha ha ha Mishaps happen all the time, but how she reacted to it by just walking off was very amateur. She's a veteran and as such she could have just said there's an audio problem so I am just going to sing off the cuff now and made it a great moment. She missed the opportunity right in front of her to be amazing after a mishap, but instead she sheepishly ran off the stage and then later accused the producers of sabotage. Ugh!!!
Ooooh, you wicked, wicked monkey! Robin Williams in Mrs. Doubtfire