I wish I could remember where in Lileks I saw that bit that he wrote about why Lucas did Return of the Jedi the way that he did, but this quote of Dan Vebber emailed to me by Erick Erickson has its own charms:
But aside from what we see onscreen, the Ewoks are miserable little creatures for a completely different reason: they are the single clearest example of Lucas’ willingness to compromise the integrity of his Trilogy in favor of merchandising dollars. How intensely were the Ewoks marketed? Consider this: “Ewok” is a household word, despite the fact that it’s never once spoken in the film.
Of course, the advice that I got right afterward from a third party – which was to just get over the entire Lucas betrayed fanboy thing – was probably very sensible. At least, I bristled at it, which is usually diagnostic.