In a modern literary novel, the plot is driven by the characters, and this is how it should be, because it is their fictional inner lives with which the reader is concerned. The reader is provided with direct access to events in the minds of the characters and can understand the plot as unfolding naturally from them. Not so in Austen. Her focus is on how her characters react to events, not on their capacity to cause them. The happy endings, like the intermediate trials and tribulations, are always dei ex machinis (also a standard feature of the romance genre in general) – that is to say, they ring somewhat false. This is because Austen’s plots are author-driven – they proceed according to what she wants to say, not according to what her characters want to do. So unexpected things are continuously happening: the characters are always doing strange things offstage (like jilting lovers, or eloping, or falling into terrible illnesses) that seem not at all realistic in terms of following from what we have been told of their motivations and dispositions.
...There are also Austen’s positive illustrations of what virtuous conduct looks like. Here one sees why the plot is so firmly in the author’s hands, not the characters’: Austen is primarily concerned with setting up particular scenes – moral trials – in which we can see how virtuous characters behave in testing circumstances. These lessons to the reader are what she gave the most exacting attention to. This is where her words are perfectly chosen and sparkling with intelligence and deep insight. These are the parts that she really cared about. The rest – the rituals of the romantic comedy genre and ‘social realism’ – is just background. (emphasis mine)
This is why I always object so strenuously when someone chooses to characterize Jane Austen's books as romances. Modern romances are author-driven in that the author is setting up situations to which the characters (and, vicariously, the reader) respond sexually. Austen "set(s) up particular scenes – moral trials – in which we can see how virtuous characters behave in testing circumstances."