In the actual case with Tesla, the driver of the car that was in front of the pile-up was not at fault IMO. But there were a bunch more cars behind, and at least some of those slammed into each other because they didn't maintain proper distance, according to the police.
If there is an obstruction ahead, the safest scenario is to change to an empty lane ('empty' including safety distance) or brake in your lane to avoid hitting it. If you have some other problem you should probably brake slowly and change lanes to the outer edge of the road whenever there are safe gaps.
I would probably be off the gas or braking based on movement of the car in the other lane as part of driving defensively, though i don't think there is any 'obligation' for me to do so.
The behavior of the Tesla would also strike me as rather odd (assuming a right hand drive country unless there is a off-ramp coming up on the left) as it appears to be pulling over to the wrong side of the road.
