> none of them invented Docker

I think that depends on what you mean by docker. Lots of similar things existed before, just less formalized and less centralized.

Which makes me wonder, would docker have gained traction if they didn't offer free registry services?

But there's a reason why Docker was so successful - a single file that could define a deployment and tooling to build it into a runnable artefact was incredibly useful. From the future tech useful.

If you can name these other similar solutions created by charities I can probably me more specific.

I think of Docker as a well executed and well-timed formalization of existing tools. It put a name to a collection of engineering concepts. This is why people can build Docker in N lines of shell script. Jails existed in the late 90s. IaC had multiple options before Docker.