Obviously, all kinds of mould grow in damp conditions, but it is not strictly true to say that poor ventilation and overheating are the main causes.
If houses are properly insulated and keep at an even temperature of at least 19 degrees centigrade, then opening windows for five to ten minutes in bedrooms and sitting rooms, and for 15 when the bathroom is damp after showering and either using an extractor fan when cooking or airing the kitchen when you have finished, should be more than sufficient to prevent black mould.
However, it is easier for mould to develop than it is for you to get rid of it! So I suspect the problem is that the housing we hear about has had mould for a long time, some attempt has been made to get rid of it, the mouldy walls repainted and then the mould just comes back unnoticed to start of with.
In the present sad case, both parties cannot be being strictly truthful, as the housing authority says they have not been clearly informed there was a problem, and the bereaved parents say they have repeatedly begged, cried shouted and so on.
Frankly, my money is on the housing authority not being strictly truthful here, as they do not seem to have claimed that they actually went and looked at the property in question, which is surely the first thing a landlord should be expected to do.