Games are fantasy worlds and they have nothing to do with reality.
Actually they do, they are part of culture and experience. And if in all or most the experiences you get as you grow up women are shown as sexualized no-brain, it has an impact on the way you see and asses other people intelligence (or your own).
No game or movie or book will do that by itself, but multiply it by thousands of those, everyday, and in the end the message seeps in. That's simple opinion manipulation.