I think it's the complete opposite - IC was created (rightfully IMO) by technical contributors to reject the idea that the only way to progress in your career and make a bigger impact is to go into management. It's just the recognition of a parallel career path

If that was its purpose it failed. Many (most?) companies have no progression path other than management, but they'll happily call you an IC.

It’s nothing to do with Agile. It’s just a short way to say “employees who are not managers.”