If a prosecutor bets the whole ball of wax on a first degree murder conviction, when the evidence may only support (or more likely support a conviction on a lesser charge) he risks confusing the jury and getting a loss. That is what I think happened here.
I was just listening to Judge Napolitano on Fox. He stated that prosecutors usually go for as much as possible, since they are elected in FL, and the populace likes that. He said that it would have been better for them to make their top count aggravated manslaughter, so now she will probably walk tomorrow.
I don’t know about confusion. Maybe these jurors who were sequestered for two months and probably irritated by now were annoyed by the fact that the charges didn’t warrant a capital murder case since there was only circumstantial evidence.