I think a big part of it has to do with the constrution of the wheels on the rover. They are a wire mesh with a bit of reinforcement. You can sort of see it in one of the pictures in the OP. This means the loose, dry dirt would flow up through them a little, then fall back down, leaving much less of a footprint that the average ATV. It would sort of be like pressing a wire strainer down onto a mound of flour. The boots were more or less solid on the bottom, so the dirt had to compress. Does anyone have the ground pressure for the rover? For about 300 pounds of astronaut in suit (50 on the moon) with a pair of 14 by 6 inch foot prints, I get about 0.3 psi for ground pressure, though I'd feel better about it if someone could confirm/correct it.
I'm Not Evil.
An evil person would do the things that pop into my head.