extrapolation- change the end of the story

I'm not exactly sure what you are asking. I'm reluctant to say that Twain ended the story artificially. Twain had said, "When one writes a novel about grown people, he knows exactly where to stop – that is, with a marriage; but when he writes of juveniles, he must stop where he best can." Things end the best that they can for Tom. Tom gets the girl, he is a hometown hero and he gets rich. It sounds too good to be true but Twain does leave us with lingering doubts about Tom. Has he given up trying to be a Robin Hood? I'm not sure.