What level of experience did they have vs what you think was needed for that dive? What were they missing in terms of what they needed to safely do that sort of dive?
I had an interesting conversation with the guy who originally explored that section of the cave. He told me that he took a very well known, highly experienced, deep cave explorer back there shortly after finding it. That highly experienced explorer got stuck in the same manner that was the likely precipitating event that led to the chain reaction which took those two guys out. The original explorer told me that during the problem, he thought to himself "****, I just took out so and so".
I don't know first hand how much experience those two guys had in Eagles Nest, but I know how much experience I have in that cave (not much, but at least 50 dives, including several in the 6-7 hour range and dozens of dives to the end of the upstream/downstream lines and a few dives to the Abyss room) and I still haven't gone back where they were trying to go.