Why do I see people stating that Obama won b/c of his race or b/c of Affirmative Action?

Rationalization. These people just don't want to admit that Obama was the better candidate and that an overwhelming majority of Americans support his policies. It's kind of like some Seahawks fans blaming their Superbowl XL loss on the refs. Also there are some racists that actually think that the only way an African American can succeed is because of Affirmative Action. They usually blame their own failures on race. Thankfully, this is a small minority that keeps getting smaller.