Look at this text please:
Eventually, I lowered the window of the car and he said "Could you help me?"
I took the risk. He explained that while he was driving he had had a terrible argument and had decided to get out of the car.
I understand both past perfect: The man explained something that had happened before he lowered the window. But why "was driving"? This action is also "past of the past", even it was not finished at the time of explaining. He was not driving, because he was out of the car.