Yeah, that's good example of how fast it can happen. I've been upside down offroading (Baja Bug), and I can attest, it will happen in an instant and when least expected (terrain-wise).
All the vehicles in th vid were climbing that hill in WAY to tight of succession and should have been spaced further. Fortunately noone was follwing this jeep as closely as the preceding vehicles.
All it took for this Jeep was:
1. A little downhill (backward) momentum.
2. A depression for the rear driver-side (downslope) tire to fall into.
3. The hard breaking that shifted the COG to the rear and took weight off the front tires (which were locked up), allowing them to begin a side-slip down the fall line.
All in less that 2-1/2 seconds.