This looks like a case in which community opinion was inflamed from the beginning and sustained over time, ultimately forcing the prosecutor to bring charges he could not prove beyond a reasonable doubt. The evidence just wasn't there.
Investigators appear to have made mistakes from the beginning that were obvious to the public, and the politics of deflecting blame and attention to the prosector for refusing to file a "good case" led to this result. Now, unless an appeal reinstates the case the husband can't be charged - even if compelling evidence against him turns up.
Sounds like the Alabama case against him is pretty thin, too. But his life is ruined, whether he's guilty of that charge or not.