We found this link on Reddit.
So the log was a counterweight and on the ground was a noose that was supposed to snare the Predator’s leg and hoist him upwards into the spikes.
That was not obvious to us. Having seen it at a tender young age, we never thought the log was a counterweight, but rather a ram that was meant to hammer the spikes down onto the predator. Which made it amusing because Dutch didn’t line it up with the spikes, so it wouldn’t have worked in that manner.
All this time, we figured Dutch messed his trap up and fluked his triumph.