My understanding is that the Palin's were slowly going bankrupt due to legal costs from false ethics charges. Todd Palin had gone back to work on the North Slope to supplement her salary. But that couldn't keep up. The Palin's needed cash quick, and resigning was the only way to stop the bleeding.
Governor Palin was essentially forced from office by her political enemies abusing the ethics process.
That is unfortunate. I don't particularly like Palin or her politics. But I also don't like character assassination, gotcha-reporting or judging people based on what they say. I would rather judge people by what they do, especially politicians.
Academic qualifications are not high to be a politician, any politician even President (whether they should be is another story). She could be as dumb as a door nail and as long as she wasn't easily manipulated by others and followed the will of the people, I would have no problem with her. George W. Bush's problem wasn't that he was a frat boy or a C-student, but that he was too easily influenced by the wrong people at exactly the wrong time in a crisis.
If you look at the Republican field right now, Jeb Bush, Christie and so on... I think Palin would have had a chance as long as she had a vision and represented the people's (conservatives) will. Saying Palin is too "stupid" doesn't wash because conservatives value morals, ethics and character over intellect. She could even have used all the ethics charges as a springboard by playing the victim. And if she went bankrupt, so what? She could use that too. She would be a true blue conservative and you would have...
...Hillary vs Palin.
Corporate Executive VS Soccer Mom
The real reason she doesn't have a chance isn't because of 2008 or "too stupid" but because she is bad at politics. Why does she have all those ethics charges? She made too many mortal political enemies aka doesn't know politics. Winning the General is a different story, but with the right dice she could have been the nominee in 2016.