I don't suppose anyone does know exactly how many people lived in Grenfell Tower. The Council would have a list of named tenants, and access to the electoral register. Social services would have a list of children brought to their attention. Neighbours might know who lives next door, but where an entire floor has been destroyed there may be no neighbours with the knowledge. Add to that visitors caught up in the disaster, and the situation becomes horribly difficult.
As to naming names and picking on individuals, I think there is a distinction between liability and responsibility. Various contractors may turn out to be liable in various ways, and some blame may prove to attach to the Council for inadequate supervision, etc. But there is no escaping the fact that that the Council owned the building, and as the local authority was responsible for ensuring it was safe to live in. It is also responsible for rehousing its tenants.
I commented early on that officials in the Council were probably doing their best to sort things out, but there has been no visible leadership. The Mayor of the Borough turned up with the Queen; as the Council's figurehead, why wasn't she out there on day 1 supporting the volunteers and talking to the victims? Where has she been since? Why didn't the leader of the Council come out and explain what was being done and what help was needed? Given the enormity of the disaster, he might even have got some sympathy. As it is, the overriding impression is that the people who run the Council, whether elected or appointed, are simply not fit for purpose.
Rant over