How a grandmother who died after being left behind by a cruise ship was separated from her tour
So Suzanne died of heatstroke rather than, say stroke, heart failure or cardiac arrest, which does make sense in the circumstances.
I would imagine that she initially suffered exertional heatstroke due to the physical effort required during the section of the climb that she managed, and that this morphed into non-exertional heatstroke once she had stopped walking and sat down to await the return of the remaining party from the summit.
We know that most of the climb was in the first section of the walk, that the day was both hot and humid (humidity = impaired sweating) and that the first part of the route offered no real shade or shelter. She was eventually found about 50m off the walking route so may have gone off the path seeking shade.
Unfortunately "extreme" age is one of the risk factors for heat stroke. It's not clear what is meant by "extreme" but she was 80, even if we can assume that most Australians are very aware of heat and its affects on the body. I see Suzanne's family believe the walk should have been called off without taking place due to the conditions, but it seems to me that everyone else taking part managed it successfully so it looks as though walk leaders judged the general situation correctly. What they got wrong was in not recognising the early signs of heat stroke in one particular participant and therefore in not responding appropriately.
From what I have seen, the geographical situation of Lizard Island is such that the hot and humid conditions are probably standard year round with only minor variations, so if they were not suitable for the walk on that day they are probably not suitable at any time and the walk should therefore be permanently removed from the schedule. Yet everyone else who chose the walk completed it successfully, and it would be interesting to know whether any of those were older than Suzanne, so removing the walk permanently from the itinerary seems to be completely unnecessary.