There’s a lot suspicious about that fire. But, the boats don’t surprise me. There’s a lot flammable on an a boat. Canvas, sails, upholstery, dinghies and such. Some cruisers store fuel cans on deck. Wind blown flame and ashes could easily start any them on fire. Once one boats lit, it could spread quickly to others.
I was once out on a boat for a fireworks show. Some people got carried away and started launching signal flares. One descended and set a boats bimini on fire. Doesn’t take much some times.
Some stupid with a flare gun burned the whole place to the ground...
That it started in a homeless encampment? We'll never hear the full story. Never.