I don't know how lucrative it is for GM, but don't forget the livery sedan market. With the death of the DTS, the GMT-900 SUVs became GM's default offering, but I would have to think the operating expense puts them at a disadvantage compared to the MKT.

So how much of the windshield do these things wipe now?

In the video of the full run, you can see that it's raining. My guess is that the ramp was too slick and the car just slid off.