The cause....
NTSB only determines direct cause, and in this case that was obvious. Candles, curtains, flammables, burn. However, there's much more to the story and you get it in the depositions of the crew.
This was a boat meant for a disaster like this and the fact no lives were lost is amazing.
Captain wasn't interviewed by anyone but just handed the job in a two hour handover by the prior captain who knew him. Similar with the Chief Engineer. Captain wasn't even told it was a Class vessel and had no experience with one. Had let his USCG license lapse through neglect years earlier but now had an MCA license. Chief Engineer had no Engineering License as he'd been licensed as a mate. Had just taken the introductory engineering course. He wasn't informed when hired that the boat's Class was suspended.
Management was by owner's sister in NY but she didn't interview anyone. No alcohol or drug testing. No program in place for such. No procedures or policies. No logs.
All crew had turned over in a few months as was normal for the boat. Captain hired crew by doing what he called a speed lunch date, sitting in a restaurant and spending 20 minutes or so with each candidate. Then choosing. No other approvals or reference checks or anything.
Captain thought it was an electrical fire at first because all the electrical was a mess, in his words. He said he knew there was no point in making a check list of work to be done as it could never all get done, that the entire boat was a disaster when he joined.
As to candles, they were regularly used especially in the owner's suite and in the sky lounge, as the owner liked them. Also, the smoke alarm in the owner's suite was disconnected because the owner liked to smoke in there and was afraid of setting it off.
As to lights, the salon lights were out on the Monday before, so lighting issues didn't just suddenly appear on the day of.
Captain wasn't there for ABS because he needed to do work on his vehicle. Engineer was getting married on day of fire. Captain didn't keep on top of engineer's work as he said he never tried to manage a chef or engineer as they were very temperamental.
Owner spent 296 days aboard the previous year. When owner not aboard, work day was 9 to 5, but when he was aboard there might be guests in the evening and crowds would grow and would often party until 5 am.
So much more, but like many disasters, the problem goes all the way to the top, the CEO or Owner in this case. This was a boat in bad condition, mismanaged. No hiring plan just let the one leaving choose his replacement. No organizations. People far over their head in responsibilities with no help. They knew the fire alarms didn't work. Can't blame the second stew for using candles as they were used all the time on this boat. The owner made that decision. The Florida Fire, Arson, and Explosives investigators final sentence of their report read, "In addition to the above, the majority of the crew was admittedly new to the industry, not properly trained, or even very familiar with the vessel they were serving on and it's safety procedures."
This was, in every way possible, a disaster waiting to happen and just fortunate the main loss was this boat. No loss to the owner as he wanted to sell it.
The liveaboards some marinas fear aren't confined to clearly derelict vessels, but they can be wealthy in a neglected very expensive yacht.
Anyone who wants to read more detail, here is the resource.
https://data.ntsb.gov/Docket?ProjectID=100711