Darth Lars said:
I think you could explain this easily. The Empire had been intruding on the Ewok's moon for quite some time, so the Ewoks could have made the traps before the Rebels even arrived. It is not like the Ewoks would have just accepted the Empire's intrusion and not been the least bit afraid of them.
In a small/medium-sized country in the real world when there is unrest near a border, the local military gets beefed up because the likelihood of a conflict has been increased. If your country gets invaded then you would form a guerilla and you hide arms and make traps at various locations in case you would need them in the future.
You could find the Mythbusters episode on Youtube quite easily if you searched for it. Spoiler: The armoured truck gets smashed. You could surmise that the armour of the truck, like the AT-ST's, was made to withstand small arms fire - not a large pounding. The logs in the movie were also twice as long and pulled up higher.
In the Ewok movies, we also see them having beasts of burden and we can assume that they are skilled enough with ropes/vines and wood to make pulleys. Also, C-3PO's recognition of the Ewok language as being a dialect of a language known on other planets does indicate that Ewoks have come from another planet (moon) originally and/or would have had interaction with other worlds, which means that they could have imported knowledge for how to lift them up.
... and it is not like there aren't examples of great feats of engineering in real-world human pre-history.
Even with a pulley system operating at a 10:1 ratio, that would still require 4000-8000 Ewoks in order to effectively match the weight of a redwood. Even utilizing beasts of burden to do the lifting, that still amounts to hundreds of animals involved. Miles of very heavy-duty hand-made rope capable of supporting thousands of tons of weight would be needed as well. It would take quite a while to chop down several redwood trees using only hand tools, and the felling of the trees would be quite noticeable. While it's theoretically possible for primitives to find a way to hoist trees that heavy, they also have to do it right next to an Imperial base that's actively patrolled. So either the Ewoks built ultra-heavy traps unrealistically fast, or the Empire couldn't be bothered to notice or care that a horde of Ewoks was building incredibly large traps right in their backyard. Either way, there's a problem.
As for the Ewok language being known, I'd say it's more likely that some Ewoks found themselves in the same situation as enslaved Africans. Instead of coming to the moon of Endor, it's quite possible that many of them were taken from their home world. Granted, I don't see this really having a bearing on their ability to pull of major engineering feats, since as you pointed out, humans figured out all this stuff without the assistance of civilizations from other planets.
