They have to see for themselves the place where it happened. If you saw the tunnel for youself and imagined a big heavy car going too fast through there with a half-drunk driver and possibly a minor collision with another car, you would understand that it was nothing more than an unfortunate accident.
I lived in Paris for 2 years and I know the place. I would not go fast through there.
But of course the conspiracy theorists will say that the driver of the white Fiat had split-second warning of the arrival of the Mercedes and the concrete pillar just jumped out and got in its way.