My heart goes out to their families and I will certainly keep them in my thoughts. I would guess that they both had heart conditions that would have manifested at some point.
If you read the link that was provided by JP, it clearly says that 7/9 people they studied had preexisting conditions, and that difficulty in getting to them probably contributed.
It is very sad, but it is not a reflection of the sport or the race promoter.
There are people well into their 70's and 80's that race full Ironman triathlons. It is not an "age thing", it is a matter of these particluar racers having a heart condition. Sad, but true.