That still doesnt add up because the factory wiring to the parking lights is fused and the fuse is under the dashboard. A short blows it open.
Anyway
The fire there more seems like high ampere wiring suffering a dead short, the factory wiring has 2 fusible links at the positive terminal, they look like a tiny wire is joining the thick wire to the battery, its the safety burnout fuse which will melt and blowout when a dead short happens.
Electricians throw those away for some reason.