Another reason that they didn't want to convict is that most people today have been brainwashed by the postmodern left to conflate state-sanctioned executions after due process with murder - as if all killing was the same.
They do this in part because they have been brainwashed to believe that the Ten Commandments includes one that says THOU SHALT NIT KILL, but in fact that's not what it says:
Why Most People Believe the Bible is Against the Death PenaltyPACIFISTS TREAT ALL KILLING AS EQUALLY BAD - AND THINK THEMSELVES MORALLY SUPERIOR BECAUSE OF THIS, BUT THIS POSITION IS AMORAL AT BEST.
The Sixth Commandment - mistranslated as "Thou Shall Not Kill (Ratsach, Murder)"
The Death Penalty: What God (The Bible) has to say about it
The death penalty is an integral part of the Old Testament Law. It is in all five books of Moses (Genesis-Deuteronomy), and in other books of the Old Testament as well. Furthermore, the New Testament supports it.
The most common reason why people believe the Bible does not support the death penalty is because the King James Version and the versions of the Bible read by most Roman Catholics (including the Douay Version, The New Jerusalem Bible, and the New American Bible) give the Sixth Commandment in Exodus 20:13 and Deuteronomy 5:17 as, “Thou shalt not kill.” The Hebrew word translated “kill” in the Sixth Commandment is ratsach, and it can mean “kill” or “slay,” either on purpose or accidentally.
Ratsach, like many other words, has a wide range of meaning, and thus its meaning in a particular verse must be determined from both the immediate and remoter contexts.
Thankfully, the Bible has a lot to say about murder, manslaughter, the execution of criminals and killing in war, and it is easy to tell by studying all the verses on the subject that the Sixth Commandment means not to take a life unjustly. Bible commentators are not confused by the commandment, “You shall not kill.” Maxie Dunnam wrote about the Sixth Commandment in the Mastering the Old Testament commentary on Exodus:
According to Genesis 9:6, this commandment did not prohibit the death penalty. It is obvious in the Old Testament that this [Sixth Commandment] was not a prohibition against all killing, only unauthorized killing. 
... saying, “You shall not kill,” confuses people about killing in self-defense, in war and the execution of criminals,
A COP WHO KILLS A CHILD MURDERER WHO IS RESISTING ARREST WITH A GUN IS NOT A MURDERER.
A US SOLDIER WHO KILLS AN SS SOLDIER IN WW2 WAS NO MURDERER.
THESE KILLINGS ARE NOT IMMORAL, THEY ARE JUSTIFIED AND MORAL.
CONVICTING CASEY ANTHONY AND EXECUTING HER WOULD HAVE BEEN THE MORAL THING TO DO.
THE JURORS WERE NOT ONLY COWARDS; THEY WERE IMMORAL ONES.