I think it is the disingenuity...
She doesn't seem to have a strong moral compass. This allows her to say anything she wants if it gives her political advantage.
She is also implicitly disrespectful, because she tries (unsuccessfully) to sell us lies that are so obvious and transparent that you'd have to be an idiot to believe it. Yet, she persists, and I think that secretly has a lot of contempt for most Americans, except the powerful and rich. Because she has little respect for anyone that disagrees with her, she delivers a one-two punch of lies and condescension that drips with insincerity.
Although her handlers have obviously busted their asses, she cannot successfully conceal her contempt because she's not a very good actress. The result is the train wreck that you see daily.