Elon wanted to automate final assembly. Final assembly in cars is anything but final; it's most of what regular people consider "building" phase of the car where the body on a cart rolls forward and human workers attach parts to it until it rolls off at the end.

A lot of final assembly processes are already highly automated, albeit with human hands as tip of robots. Heavy objects such as entire assembled dashboard spanning an entire width of the car, or seats complete with headrest, are slid in from side riding on a carriage, often following a human hand that route cables and to confirm alignments for attachment.

Joint wears of worker humans embedded in the processes as robots are tracked and managed as well, by computer simulation, data tracking, and optimization.

Tool used, such as drills, are highly computerized as well, automatically setting and logging turns and torques, types and numbers of screws removed from the workstation shelf, etc., but they are still manipulated and articulaed by humans, as robots aren't good enough.

Robotizing final assembly is the holy grail for which Honda was doing robots since late 80s until Japanese economy collapsed and AI researches stopped. Steve Jobs was dreaming the same lights-out factory concept during NeXT years. More recently, Foxconn bought robots in hundreds at one point in hope that it will be useful for iPhone. Sony actually shipped some numbers of PS4 from a fully robotized prototype line.

The difference between them and Tesla is that they're so far the latest and about the least actually committed to it, obviously due to lack of engineering talent outside of UI software.