> Developer of such system? Company who made the car? Company who created the self driving system?

Those would in many cases be the same company. And yes, the entity responsible for injury would be the car manufacturer, not the driver or riders. Taking on legal liability for the car is part of the 'qualifications' for L3.

The specifics of what part of the system failed can be litigated if defendants (companies) need to be added to the case but in no case will the people inside of a vehicle designated higher than SAE L3 be held at fault for the accident.