Look at a picture of what the top 10 smartphones looked like the day before iPhone launched and then again a few years later. That is what category defining means.

They didn't take whatever was out there in the market and copy it/make it incrementally better. They started from scratch and built something drastically different and better than the rest. Same for iPod (yes there were plenty of cheap MP3 players out there, but none of them were comparable), Airpods and all the rest.