Do I think it is a crime that this father forgot about his toddler strapped in a car seat in the back of his car? Yes.
Did he purposely plan to leave his child in the backseat of a sweltering car for nine hours till he met his death? No. But neither was the one who struck another vehicle in an accident that took another's life. Negligence, wrongdoing that results in the harm of another is criminal.
It sound like the father that forgot he had a toddler in the backseat of his vehicle did not have his priorities in order. His main concern from the time he strapped the kid into the car seat would be to realize he had precious cargo on board and his first point of concern should be getting the child transported to a safe location before anything else take precedent for the day.
How in the Hell do you forget you have a child strapped in a car seat? How???????