You are assuming perfection. Have you considered that these cars may cause more deaths? What if a solar flare affected GPS and caused all of the navigation systems to injure or kill almost everyone driving at the same time? While that may be only a remote possibility, there are a myriad of other problems navigation systems may run into that they are unprepared for.
Certainly the people working on this are clowns that know nothing about safety countermeasures, and don't care about their whole industry going belly up if major accidents happened.
The same clowns that run software industry and regularly allow major security incidents costing millions of dollars to happen. It's not like nobody knows making a backdoor in a major networking software is not the best practice. It's just that people are people, and they are imperfect. I'm sure people that make those cars are as imperfect as the rest of us, no more, no less.
It's acknowledging the imperfection of people what makes software an engineering field instead of a hard science. It's not news to anybody.
Continuous testing, code reviews, defense in depth, etc. are practiced to deal with that. The engineers that design cars (the "hardware") are as imperfect as anybody else. So are the engineers that design planes' autopilots. Nobody relies on an engineer being perfect, and there's no need to.
