Realpolitik at work. 10 million is a small price to pay to get that off their shoes - it was a loser even if they prevailed.
It is certain the driver had his foot on the accelerator instead of the brake; it is impossible for a Lexus - or even a Veyron - to reach 120 mph as reported with the brakes on. The plaintiffs could have managed to slip enough people with no understanding of automotive technology onto the jury to blame the design or construction - we even have some of those fools active in this corner of Y!A - but that is neither here nor there in the end. Toyota understands the meaning of "Pyrrhic victory."
This is nothing new. In 1982 seven people died of cyanide poisoning after taking Tylenol. Johnson & Johnson was quite sure the poison was introduced after distribution but elected to recall all Tylenol everywhere at a cost that was never announced but probably totalled over 100 million dollars, in 1982 dollars. It was a wise decision - if they hadn't everybody would have remembered J&J for being unwilling to protect their customers... even though J&J was completely innocent. Toyota also was being smart, knowing the consuming public often is not.