God works inside real history, under datable rulers, among people with family lines and job assignments. Salvation does not drop from the sky onto a blank stage. It grows out of a covenant God kept for centuries with one people, through ordinary faithful folk doing their turn of service.
Two old priestly lines meeting in one household is the whole prior arrangement gathered up and ready to be handed on. Everything the older worship pointed toward is about to be fulfilled, and it comes through a couple who stayed faithful in a small assignment with no sign that anything larger was coming.