I hate to say it, and it’s not a shot at her abilities, but she was chosen to counteract the Dems picking Obama.
She was almost unknown until she came out of the blue.
Lieberman was McCain’s first choice. He was argued down. If he’d had his way, the only women he’d have chosen were Christy Todd Whitmann and Carly Fiorina! Palin was the only hope he had for Conservative bona fides tied up in a female, and praise the Lord cooler minds than his prevailed. That choice had everything to do with McCain, nothing to negligible with Obama.