Fanny is thoroughly vindicated in this rapid succession of events. Henry and Mary are both proven to be immoral creatures, and the education of both Edmund and Sir Thomas is completed. Even the incorrigible Tom is chastened. Virtue has its reward, and vice is either reformed or punished. Why, then, does Mansfield Park end so quickly, without dwelling on the "happily-ever-after" aspects of its resolution? For one thing, the happy ending of this novel is in part a product of luck--Maria and Henry just happened to cross paths, thus enabling the eventual marriage of Edmund and Fanny. There is no sense of inevitability here, and the rest of society has definitely not been put right. Rushworth will again marry some beautiful woman who is only interested in his money; hopefully things will turn out a little better this time, and his new wife will only engage in "standing flirtations," as Mary puts it, using a bit of a Freudian pun. Maria and Mrs. Norris are not reformed, but instead kicked out of the family circle and even out of England. Mary Crawford seems to be merely resting, and will continue her conniving ways when the time is right. Most of Fanny's biological family, too, remains in squalor back in Portsmouth. Although the good have been rewarded and the bad punished, these fates seem only temporary in many cases. No real education or reform has taken place, except in the mind of the now fairly old and isolated Sir Thomas. He will most likely continue to help Fanny's siblings, but overall the world has not been set right.
The main thing that was to be accomplished in this novel was the assignation of Fanny to a place in the social order. This has indeed happened: she is now a daughter to the Bertrams, both by marriage and by adoption. The way in which Austen ends novels by not really ending them--we don't see anything of Fanny and Edmund's married life--suggests that fixing one's social position is not the end of the story, despite the nineteenth-century belief that social position was the most important thing about a person. Do they, in fact, live happily? Do they have lots of children? Is Edmund a good minister? Does Tom Bertram die young and leave Edmund the heir to Mansfield Park? We don't know, and this lack of resolution is deliberate. The fact that Maria is ruined while Henry and Rushworth both may yet marry and are still valued members of society suggests the arbitrariness of the social order, which says little about a person's inner worth. The lack of closure is also a brilliant artistic stroke on Austen's part; the reader is left wondering about Fanny's future life, and this active involvement with them makes the characters stick in our minds longer than they might have otherwise.
The marriage of Fanny and Edmund celebrates the ideal form of love: a companionate relationship based on family. That their relationship skirts dangerously close to incest--they were, after all, raised as brother and sister--is an issue that is avoided here. Mansfield Park is not the only novel to feature such a relationship; Wuthering Heights is a more prominent example. Perhaps the close kinship of Fanny and Edmund is meant to reflect their essential similarity to one another as people. We are constantly reminded that Edmund has formed Fanny's mind; in this way, he has been a father to her as well as a brother. While again, to modern sensibilities, this seems both incestuous and dangerously paternalistic in the imbalance of power between man and woman, it also suggests an ideal for intellectual and emotional companionship. Fanny and Edmund are, almost literally, everything to one another.