I recently came up with the idea that Guybrush and co are all actors, making a pirate b-movie, and in both games you're running around on a giant filming set. Cheap costumes, continuity errors, anachronisms, mysterious dialogues (come on Guybrush, play along, that's how they used to talk back then, etc).
And a lot of b-movies have an open ending, to keep the possibility of a sequel open, thus having a seemingly nonsensical ending in LR. If this theory would be true, the third game could end with a director (perhaps Ron Gilbert himself) say something like "aaaaand CUT! Good work people, we're done."