Well, I may not know the exact answer, but I can confirm because of mass. The more mass an object has, the less control you have on it, so it can't be stopped easily. Let's take a small rock and a boulder for example. When a small rock rolls on the ground, it can easily be stopped by your hand or foot. But when you have to deal with an enormous boulder, you can't easily stop it with one just person. You'll need more people. So the answer is because the smaller vehicle has a lesser mass than the larger vehicle. (if you are looking for the answer, just look at the end.
