I'm on a techie mailing list which includes someone who has a deeper knowledge of the EV1 issues than appears in a tendentious "documentary".
GM was betting on rapid improvement of batteries. By the time they'd have to replace the batteries in a couple of years, they'd have better/cheaper/more powerful batteries. By only leasing the EV1, not selling them, they guaranteed that the batteries would actually get replaced, and not have to rely on everyone paying attention to recall notices, because everyone does not.
The improvements, alas, didn't come in time.
There was a little issue with the batteries, especially as they aged, having a tendency to what he referred to euphemistically as "thermal excursions". Maybe not Samsung Note 7 level, but still, a hazard.
That meant legal liability, increasing as the batteries aged, and the risk of those "thermal excursions" rose. When California dropped the electric vehicle requirement, GM didn't need to take that risk any more.
Yeah, the fans of the EV1 (which were many, it was by most accounts a really nice car) didn't want to give them up, but "leased", not "owned". The legal liability issue was the killer. It could be shown that GM *knew* the batteries had potential issues as they aged, because they did. The owners of the cars could promise not to sue, they could sign a stack of liability releases and disclaimers and knowledge of the risks that weighed more than the cars, and it wouldn't have made the slightest difference in the legal liability to GM. Courts and juries have over and over and over again proved that no release of liability, no matter how strongly worded, or how much the person taking the risk wants it, has any force in the face of some poor pitiful victim of a tragic event wailing in court about the horrible, mean, nasty corporation who sold them the dangerous object, even though their signature is next to every paragraph spelling out each and every hazard, and saying that they swear on a stack of Bibles that they completely understand and accept the risk, and absolve the company of any liability.
I'm not anti electric car. I drive a Prius, and for my next car, I'm seriously considering a Tesla or Volt. But the EV1 issues was far from just the "Evil corporation destroys a non-polluting car because they make money polluting" crap from an exceptionally bad "Captain Planet" episode that's usually presented.