The use of the stereotype represents the ideology used for this ad. Its purpose is to make the message very simple to deliver which basically is the advantage of using stereotypes in advertisements.
The message directly delivers the idea that blonds are beautiful but unintelligent which is not the case in Mercedes cars. The dumb blond used in this as represents a symbolic sign (blond lady=dumbness). The phrase that appears at the end of the commercial "beauty without brains," emphasizes this idea furthermore.
Mercedes also tend to use intertextuality as it also borrows other stereotypes, such as depicting the librarian as an unattractive lady that wears eyeglasses (the eyeglasses are hanging on her chest). The language used in the ad is simple and to the point. Humor is used as a message appeal in this ad which attracts a very large audience who likes funny commercials.
Mercedes uses the pre-emptive strategy in which it differentiates itself from car companies that focus only on looks and neglects the functional aspect. In this way, it emphasizes the point that Mercedes is not one of those companies that deals only with looks. This ad is not only targeted to a local market but is rather globalized as it solves a misconception that is globally perceived.