McCain's pick of Palin was a cynical ploy to pick up women voters.
The Democratic Party was coming off a highly contested primary that would have seen Hillary Clinton be the first woman to run for president for a major party had she won. Many of the women who had supported Clinton were quite publicly disenchanted over coming so close to nominate a woman and losing out. There was even talk of women Democrats not supporting Obama as some sort of protest.
It was in this environment that McCain developed a short list of vice presidential candidates who were women. It was based on the Republican theory that minorities don't make thoughtful decisions in elections, but merely prefer to vote for one of their own kind.
McCain didn't find out more about Palin because the only credential in which he was interested was that she was a woman, and he thought that alone would secure the woman vote and take him to the White House.
Making the choice about her based solely on her biological sex without regard to her intelligence or competence does not comport with any feminist ideal. And we continue to see the legacy of that choice.