A 1 kg fire extinguisher is not going to stop your car from burning. It is going to help to stop flames from burning you if you are trapped, giving other people more time to get to you and get you out of the car.
General rule I like to use is, if in an accident and your seatbelt locks (or you're stuck in a harness). Can you reach and retrieve the fire extinguisher from where it is mounted. I've got short arms and can't reach it if it was under the front lip of my passenger seat, so I've mounted mine on the passenger side of the tunnel, behind the passenger seat, where I can reach with one hand even if my hips are pinned in seat.
That Ferarri was caused by the driver losing it sideways over the dirt and rolling it on its side, then a small car fire (as Ferarri's do) / hot exhaust fire started which sparked a big dry grass fire and the rest is history.
Though, most likely whatever event that was at didn't require extinguishers, hell... probably didn't even need helmets.