there were definitely probably multiple points of failure. for one, the batteries are supposed to be insulated and weatherproofed. if it was seawater, then a lot of water got on the car for an extended period of time until something seeped through the cracks.

My bet is that it was a faulty battery. especially with lithium batteries, if they are not put together rights or they are improperly charged they will literally blow up like a balloon before releasing a continuous fiery explosion. well I'm not sure about lithium ion batteries, I know with lithium polymer batteries this happens if you leave the battery up full charge and then proceed to not discharge it and let it sit for days or weeks. it's why the so-called hoverboards and electric skateboards were banned in the cargo holds of planes: people were buying a bunch of Chinese knockoffs and not properly taken care of the battery, which led to the fires that we know and love.