If Docker didn't want this to happen, they should not have given everything away for free and then started charging money for it years later.

Also keep in mind that Linux containers are based on open source kernel technology and Docker was just a friendly layer on top. Anyone else has always been free to build their own friendly layer on top. All that's changed is that those alternatives are now more compelling.

What precisely did the creators of Podman Desktop do that was unethical? I'm not sure if by "ripoff" you mean "copyright infringement" or something else.

That is absurd. These “ripoffs” are entirely enabled by the licensing/donating of the technologies that underpin Docker, let alone Docker Desktop.

Using open source as intended is literally the opposite of a "rip-off."