1) The structure seems to have held up quite well actually.
2) Didn't these ratings get tweaked recently to keep up with the safety advances (i.e. A 2 Star today does not equal a 2 Star from yesteryear.)?
3) Given how well the passenger scored... I bet (because I cannot find the info at the link) the driver dummy slipped and bumped something.
IMHO... these tests are not the most perfect, because the sample size is not ideal (i.e. What if the dummy was placed in the car more crooked? What if the belt was not cinched as well as it could be? What if the fabric material vs the dummy's skin is more conducive to sliding on one brand vs another? Etc.).
From that video... I think I would be plenty happy with the results as the driver. When I read the thread title I was expecting the dummy's head to smack the windshield or something spectacular.