It's either changing 3 lanes to the right or 1 to the left. In case of loss of control, in this case with the car coming to a stop very quickly, it might be better heading for the left lane, instead of getting stuck in the middle or second lane from the right.

It’s almost impossible to rear-end another car without being at least partially at fault. The lane change from the Tesla was obviously dangerous, but the first car to collide with it had sufficient warning and time to react. You can see that they did react, but they obviously didn’t expect the Tesla to come to a full stop, which is why the first collision took place. I believe the legal term for this is contributory negligence.