Several thoughts
1-The economy
2-The car is priced quite high vs its real competitors.
3-The derivative styling will hurt it. I love the Box looks but many folks want a fresh design or the they write the car off.
4-Marketing and sales-I am sure Porsche has more margin in the 911 line. Ditto the Cayeene.
5-The economy
6-The green movement. Those guys simply hate sports cars, even if they get 30 MPG.
7-The economy, did I mention that yet?