Though I agree that with a few minutes notice it would have been nigh impossible for the Ewoks to have cut down and then raised those trees into a position *just* to smash the AT-St there may be other possibilities- after all, we will gladly go on and on about the lives and cultures of character and races in SW we *like* but I can't remember seeing any discussion on the Ewok culture (short of the Ewok movies which though I maybe watched when they came out I can't say I remember).
So- the Ewoks live in those elaborate tree-houses right? Somehow they manage to get all the materials up to the levels of their dwellings. Do they climb up the trees carrying lumber on their backs? I doubt it. So logically one can assume that they have worked out a primative engineering system allowing them to raise materials to the level needed to build. The simplest way to achieve this would be a counter-weight system- cut down a medium-sized tree, attach ropes to it, loop the ropes over high branches and then collectively hoist. The Ewoks were advanced enough to have hang-gliders, etc so they have some basic engineering thought.
Anyhow, whatever the exact un-seen construction methods were, let's say that they develop their 'neighborhoods' at the same time like much construction in our world. They very well could have been in the middle of constructing an Ewok sub-division when the Imperials showed up. So construction stops for a bit but they heavy equipment wouldn't have been removed- just secured somehow.
Then imagine the creative little teddy bears thought "Hey! If we were to trick some of these bad guys into following us into our construction zone, we could use our primitive equipment to our advantage and they'd never know what hit them!"
The rest, as they say, is history.
Dear God- did I just *defend* the Ewoks. I MUST be getting old!
