He was just lucky, not so much skilful. One thing that I have found is that even if the depth isn't too deep, if it is flowing, there is a certain point where the speed of the water will get under the 4wd and float it, and then you're at the mercy of the flow and where it takes you. Stupid - Yes, Lucky - Yes, did those following try it - I doubt it! Would I do it, no.
People in cars trying to cross water is dangerous enough, but they are less likely to try it than 4wders, who unfortunately, are over-represented in such mishaps and fatalities. Rule one is always to walk it, and if your jocks get wet, carefully consider your options and the potential of catastrophe. The other advantage of using your jocks as a Plimsol line is that the water around here tends to be very cold when these situations arise, and cold water tends render the contents of jocks much smaller than they are perceived to be when someone actually makes a crossing like this. Makes you less brave, or stupid, in hindsight, depending whether you make it across or feed the yabbies.....