A perfect storm:
inadequate tow vehicle (looks like a BMW 5 series wagon), probly rated to tow 1500-3500 lbs, if that, pulling a 5,000 + trailer/car combo, was probably using cruise control so wasn't able to respond instantly, towed car looks like it's back too far on its trailer so that the tongue is not properly loaded, and it looks like the driver finally hit the brakes, the trailer had inadequate or no brakes and "rear-ended" the tow vehicle and w/nowhere else to go, fell over on its side.
Thus far my experiences in my new Touareg "tow rig" have been totally benign (knocking on wood). I'd say Martin's set up shd be able to handle most anything!