Because nobody was willing to spend money to try.

If you had a time machine and a few million dollars more than the tax write off and perceived brand damage they might well have done the same before the materials were destroyed.

Although, part of the reason coyote v acme did so well was the outrage over batgirl being cancelled.

I feel like Coyote vs. Acme felt a lot more novel, which got it more attention. There are only a few hybrid real life/animated hybrid movies out there and they are mostly highly regarded. This was a novel premise to that idea, so there was an audience interested in seeing the movie.

In contrast, there wasn't as big a pent up audience for Batgirl. Superhero fatigue is real and having a woman lead has been shown to be underperforming recently.

Two major issues:

• Batgirl would conflict with the new DCEU
• Batgirl was still in post production, so still needed a lot of work to be "finished", unlike Coyote vs Acme which was apparently completed when it was shelved.

Source: Screenrant

If I was to learn that the "they're not going to release it" hype around Coyote vs. ACME was, at the root, a deliberate, well guided marketing campaign, I would not be the least bit surprised.

The same may not be true of Batgirl because that was shelved first, and merely provided the powers that be the idea for marketing the ACME movie.

I know they were shelved at the same time but I’m not sure where Batgirl was in terms of production. I believe Coyote vs Acme had finished and was in post, hence some of the outrage but I don’t know about Batgirl.

It could be. Start a movement.

I also, maybe naively, think CvA is better known than batgirl? Otherwise I think people mostly have it.

Because it was bad.