It was started by people doing a giant business consulting project, for Chrysler. The Agile Manifesto came out of (some of? all of? I forget) the signatories' experiences working on the Chrysler Comprehensive Compensation System, using the Extreme Programming methodology. How well did that work out?

From the Wikipedia article:

"The one-year delivery target was nearly achieved..."

"A few months after this first launch, the project's customer representative—a key role in the Extreme Programming methodology—quit due to burnout and stress, and couldn't be replaced."

"The plan was to roll out the system to different payroll 'populations' in stages, but C3 never managed to make another release despite two more years' development."

"Frank Gerhardt, a manager at the company, announced to the XP conference in 2000 that DaimlerChrysler had de facto banned XP after shutting down C3..."

I've seen it argued that it failed a lot more quickly and cheaply than most comparable projects at comparable companies.

The key word there is still "failed".

Some writing from Martin Fowler about the project:

https://www.martinfowler.com/bliki/C3.html

Would that be the same Martin Fowler who largely made his reputation on the basis of Agile, and thus has a major incentive to make it look good?