The public killed the electric car. No one would pay for it. GM couldn't afford to keep making them at such a low cost, so they stopped. Everything else in the film is irrelevant. If you can't make money on a product, you'll go bankrupt.
I don't agree with tax breaks, only because I don't believe in income tax. No one should pay more or less tax than anyone else for any reason.
No it would not have saved any electric car. No one would purchase an EV that gets 120 miles a charge, at $60,000 dollars, that can only hold 2 people, and only has 10 foot of cargo space, takes 6 hours to recharge, and requires a $1500 charger. GM was eating all that cost, and it was killing them. If they passed that cost onto the customer, no one would buy it. GM lost $400 million in the EV1 project. No battery would have saved it.
If you believe government should dictate what product a private sector company should make, that is a communistic view. California had no right whatsoever to tell anyone what product they must sell. GM should have refused to even try and make an EV on the moral, and constitutional grounds alone.