Sarah Palin..., Why did Bush say she is not qualified to be President?

From an outsiders point of view all your past and present Presidents have come across as being bery diplomatic and qualified for the job. I'm sure she is a nice person but whenever I see or hear Sarah Palin on TV I want to run a mile. She is a bit over the top and never stops talking. Her motor mouth and high pitched voice would make Americans even more disliked in the world. (I'm a New Zealander)