The steam tractor’s hitch gives it a tremendous mechanical advantage because it is lifting the JD’s rear end upward. Therefore, the JD’s has very little ground pressure on it’s rear wheels.
On the contrary. . . The empirical evidence is that the JD tractor had plenty of ground contact and pressure, because it actually dug itself into that ground. What it needed was traction. . . And sufficient area on that traction for its power to not dig itself into the ground . . .
I suspect the tires on the JD may have had too sharp a tread that acted as shovels to break the ground, digging in and spreading the soil outward, to its disadvantage. The tractor would have been better off with racing slicks in this tug off.
Look at the metal tires on the Steam Tractor: they're flat, with little flair to dig in.