So you suggest doing nothing? Letting the car continue until it leaves the road at the first corner? Potentially causing a head on if there is no dividing barrier?

Tesla driver did the right thing, and is a hero in my books.

Call the police, stay nearby with warning lights perhaps? You could even take the middle option and slow them down to a safe speed.

It's an extraordinary situation, there are no well-proven answers here.

It is however well proven that stopping on a highway kills people, if they had caused a pile-up this would be a very different story.

Its baffling to me that you and others (downvoting) are so convinced that this was a safe action because the outcome was good this time.

It's not a safe action. But it's also not safe to do nothing. I think the driver made the right call (and with the benefit of hindsight it was in this case.)

Doing nothing would have resulted in a high speed accident with certainty of 1. This could have involved a head on or left wreckage on the highway. The driver took a chance on a risky intervention and it paid off.

Sometimes it can still be the safest thing to do. It sounds like that was one of those times.