Well, we don't know what made JA briefly accept Harris B-W, who seems by all accounts to have been what would in her day been called a bit of a booby - younger, shy, physically unattractive, his only two 'good' points being that he was the younger brother of two of her friends, and rich.
Biographers usually surmise that it was a vaguely Charlotte Lucas-ish desire for an establishment and to be able to offer Cassandra and her mother a permanent home, followed by an overnight realisation that marriage without love would be a disaster (as she says more than once in letters to her nieces).
But we don't know, only that Jane told HB-W she had changed her mind first thing in the morning after accepting him the night before, and leaving the house immediately. Cassandra destroyed all the letters that might have talked about it.
but then we have Willoughby who is able to gallivant off and marry an heiress having practically been engaged to poor Marianne.
How widely known is his relationship with Marianne, though? It takes place in a remote part of the countryside in a fairly confined social circle, and by the time he and Marianne re-encounter one another in London (where being seen repeatedly dancing with her in public etc etc would certainly have given rise to a general expectation of their engagement), he's gone all distant and polite and is no longer corresponding with her.
Similarly, I imagine Edward would have been forced to be more upfront with himself about his own feelings and/ or the risk of exciting feelings in Eleanor if they'd met in society London, rather than in a private family gathering at Norland...?