I would be interested to see what would happen if the hitch/attachment point on each piece of machinery was at the same height instead of the hitch on the steam engine being markedly higher even before the JD started digging into the ground. The higher hitch/attachment point on the SE would tend to help the SE lift the JD's tires off the ground while the JD would be pulling the SE's wheels down into the ground with even more force than the weight of the SE alone.
Who knows? There may be some "hitch height formula" they've devised to try to keep things more equal during these head-to-head pulloffs. It seemed the JD was completely outmatched by that old behemoth.
It would also seem to me to be an advantage of the steam engine's "tires" that they wouldn't flex like the tires on the JD.
Do they put fluid in pulling tractor tires like they do in farm tractor tires? I would imagine that steam engine weighs considerably more than that JD tractor, perhaps even twice as much if not more. I bet one wheel off that steam engine weighs more than both rear tires on the JD. In the case of these two battling machines, I would stay the steam engine has a big advantage due to its immense weight.
It might also be largely a matter of design. The JD is obviously capable of spinning its wheels at high speeds while the SE engine is not. The SE is probably really not capable of travelling any faster than it does in this video: the rear wheels can only turn so fast no matter how much power is applied to them.
Here's a video of another steam engine pulling a sled as far as it can and it finally just kind of runs out of oomph without the wheels ever spinning at all.
I would also note other descriptions of the original video refer to that particular JD as a "drag tractor" and it doesn't really look like a pulling tractor, so I'm sure it's been modified for higher speeds rather than for brute torque and traction so it would be at even more of a disadvantage in a pulloff no matter how many HP it boasts. It's possible the same tractor in its original configuration would have fared better than this modified one. As modern tractors go, it's pretty small.