There's also the very good chance it started as a galley fire. Those boats have outboards, so likely any engine related fuel is outside of the the main cabin (unless a spare tank or the main tank or even the engine was being stored on the floor of the cabin while under way, big goof). But the galley stove may be an alcohol or butane (my F-27 has a two-burner alcohol stove). A goof fueling/prepping the stove or cooking up lunch can cook the boat - out of control flame on the stove catches interior materials, etc, etc, etc, Even if the boat itself resists burning, crew bags, towels, charts, rolls of paper towels, cushions, or anything else stowed below can stoke the fire.

The main hull doesn't have to burn completely to detach from the akas/amas, it only has to burn to the point of structural failure around the attachments.

Maybe we'll see a write-up in the Boat U.S. insurance magazine...