Yeah no, that's not a weatherproof electrical box. It's not impossible the factory didn't install it but that can be rectified.
It appears as if the automotive circuit breakers took a big load and gave up the ghost and died a quick death.
A closer look at the last photo where the cable goes through the floor looks very suspect. I wouldn't doubt if that cable wasn't squashed between the floor and the frame rail or cross member there.
Whatever you had running that needed the 12 volts was more than that mess could handle. What you have pictured did well to hold long enough to make the interior light work.
Someone will come along and no doubt tell you exactly what happened to cause the problem.
Good luck with the dealer and impress upon him that you are very lucky to be alive.
2013 Voltage 3800, 2012 Chevy 3500 HD
2010 Yamaha V Star 950
2009 Yamaha Raider
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