Something that is not discussed is that the majority of the population had fled. Those left behind (and consequently died) were slaves and hired help. They were left behind to watch after their masters property.
CC
Left behind servents and slaves caring for property were certainly there. Also poor people who had nowhere else to go. Possibly a few opportunists who thought that they could pick up some loot while the population was mostly gone. All kinds of motives and types could have been there when the ash bomb/pyroclastic flow hit. I look forward to seeing the results of the larger DNA analysis.