I would not surprised if _hundreds_ of people have "invented" a fully digital media-free audio player years or decades before Apple perfected it into a consumer device.
This is a world of billions of people. Billions. The romantic idea of one man/woman inventing something - without another man/woman inventing the same unknowingly - is just not realistic for most things.
I had a conversation about the idea in 1987. Hell! In 1993 me and a group at a company were spitballing ideas for the video technology we had and came up with a home DVR. Hard drives were not quite up for the task for that so the idea got shelved.
To quote Heinlein:
“When railroading time comes you can railroad—but not before.”
This is a world of billions of people. Billions. The romantic idea of one man/woman inventing something - without another man/woman inventing the same unknowingly - is just not realistic for most things.