Fault implies blame. Someone consciously conditioned these dogs to behave this way, to somehow learn this kind of response is an acceptable one and not out of the realm of normalcy.
It’s not all conditioning, the potential to snap is innate.
Good, careful owners, high quality training, sweet dogs. Andsometimes they go off. Like the family dogs who killed the two small children in Tennessee, savaged the mother when shelay over her babies. The ones in Canada who tore a quiet calm child out of his sister’s arms, people they knew very well. Conscientious owners who thought good training and good treatment would make good dogs.