If Wookies are prefered on Endor, They might be colonists from long ago. Wookie Amish who wanted to get back to their primitive nature ('Witness'). Alternativey, they could be survivors from a shipwreck 1000's of years in the past.
When I saw the Ewok, I thought "Rocky!" There is even a Bullwinkle. It could give the creatures an entire other dimension of action.