Because she has been in politics for for 30 something years, been on the national stage for 20 something years, and has been "the next president" for roughly 10 years. This wasn't one hit job, this was decades of concentrated work that eventually broke the camel's back.
How is "I'll do exactly what the establishment tells me to do, just like the last couple figureheads, except in a $10K Chairman Mao pantsuit" a challenge to much of anyone?
The country has a not so comfy history with black folks, yet men and women have lived together for eternity, so why didn't Obama get it perhaps 100 or 10000 times worse? Surely you're not a racism denialist? Perhaps no one accused Obama of being a criminal because... he isn't? I mean I never voted for him but I can respect him, he's a wise constitutional scholar who probably deserves a supreme court appointment to an empty liberal seat when this is all over. I disagree with him on many issues but he's no crook and he's reasonably wise. He got teased, essentially, about a technicality of being born in a foreign country and being muslim which frankly don't matter and never turned out to be a problem and never went past offending people on twitter.
Palin was hated in the mainstream media, but it was just a generic Quayle style two minutes hate. How come no one provided any evidence of her crimes? Perhaps... there were none? Could there possibly be any hatred hotter than the DNC controlled MSM's hatred toward Palin, yet there's nothing but sophistry against her because she's clean? I wouldn't describe Palin as being a bright bulb or a beacon of wisdom yet I voted for her, she's not that bad.
[1] - https://en.wikipedia.org/wiki/Alaska_Public_Safety_Commissio...
There could have been a vast conspiracy to frame the Unibomber or Al Capone or John Dillinger or Nixon. No one can explain why them. Therefore I think it infinitely more likely they were just crooks.