I put the failure of the prosecution down to overconfidence. As observers of the case leading up to the trial we all convinced each other that Baez was a fool, and that the state of Florida had it in the bag, the prosecution lived in a similar bubble of confirmation bias. Based on what the jury saw I believe they made the right decision, I believe Casey killed Caylee, but is it possible that she drowned or met some other demise which was covered up? Yes it is, and that is reasonable doubt. I also think Ashton's behaviour in the courtroom, in particular during Baez's closing arguments harmed the prosecutions case, and may have even been the tipping point for the jury. Also there was so much prejudicial media coverage of the case before the trial that picking the jury had to be strict to the point where they had to say they hadn't watched all the coverage or formed any kind of opinion, which I can't even imagine would have been possible in Florida unless you lived off the grid in a cave. JMO.