These people had listened to all the perverted shit "evidence" for weeks....cooped up with each other...probably getting more annoyed by the day, and some even coming to hate some of their "fellow jurors"
...all they wanted to do was go home.
If you listened to the "foreman" he admitted that he was getting concerned about the welfare of his dogs.
So....in order to avoid having to go thru the "evidence" again, and to get away from each other....it was determined that the easiest way to do this was simply let Casey go...
...and that's what they did.
I hope the jury foreman can live with the fact that he put his dogs before justice for little Caylee. Nauseating.