I've been following the news and this thread from the beginning, and I think the mods have done an excellent job managing this discussion. The recaps have been particularly useful.
It seems to me that we have reached the point of diminishing returns from further speculation until more information is learned.
We know for certain that a fire on the boat prevented the escape of all 34 people who were in the passenger berth below. We can infer with good confidence that the inability of even a single person from below to escape suggests that their escape was made impossible by some circumstance. With similar confidence, we can say that this must have been due to one of three circumstances or a combination of them:
- toxic gases or a lack of oxygen that quickly incapacitated those below, possibly even before they awoke,
- rapid growth of the fire to such an extent that [edited to add: or failure of fire detection devices to raise the alarm before] both possible exits were impassible at the earliest moment of detection by those below, or
- an explosion (established as unlikely based on the lack of explosive materials in the relevant portions of the boat).
In the current absence of forensic information about where the fire began and how it burned, we are unable to determine which scenario is accurate, though analysis of possible causes has been informative. There seems to be consensus that the most likely cause of the fire was electrical in nature, either battery failure, defective/degraded wiring, or both. But again, in the current absence of forensic information we are unable to determine which scenario is accurate.
IMHO, we are now left to wait for additional information from the NTSB. Without it, I think further speculation is unlikely to be useful, though I would be happy to be proven wrong.