Looking at the details of the case, it is hardly black and white.
The "Stand Your Ground" law came into play with regard to self-defence.
“Stand your ground” just means that you have no duty to retreat before resorting to force. You still have to reasonably believe that the use of deadly force is immediately necessary to protect yourself from the other party’s use of deadly force against you in order for self defense to apply.
Logically, someone must have held that view. Maybe the Attorney General reviewed the case.
Appreciate the simplified explanation for my retiring brain cells.