Other Fuel System Tank Assembly problems of the 2008 BMW 335

I owned a 2008 BMW 335i for about 4 years. Last month I was driving the car home after picking it up from dealer. I brought the car to the dealer because the crankshaft sensor failed and also went for the battery recall. Driving back from the dealer back to my apartment was about 30-40 minutes. So right when I pulled into the apartment parking lot, I noticed my trunk was smoking through my rear view mirror. I quickly tried to park somewhere empty, then I got out and I saw the rear end of the car was flaming up. It took less than 20 minutes, the entire car was covered with fire. Since the fire started from the rear, I am sure that's the battery wire connection that caused this. I am frustrated because I dd this car and only happen after the service from the dealer. Also why BMW design and position the freaking battery and wires behind the gas tank?.