That’s either a patriotic suicide truck driver bomb, or a poor sap that didn’t know it’s cargo.
Either way, that’s one heck of a longterm operation behind enemy lines.
Getting a truck.
Getting explosive materials.
Getting materials into truck , so it passes the x-ray machines on bridge (unless bribed?).
Getting a sap driver/suicide volunteer to deliver the cargo.
And finally, with the unlikely coincidence of it exploding, just as it’s passing a fuel train…that’s incredible timing.
If it was a truck bomb.