Foveon didn’t disappear, but it remained a niche technology, mostly in Sigma cameras.

The main reason is that its practical advantages were not compelling enough for most buyers. While Foveon captures full color at each pixel location, most photographers care more about spatial detail than extra chroma information. In common output formats like JPEG and MPEG, color information is often stored at reduced resolution anyway, so some of Foveon’s theoretical benefit gets discarded in normal workflows.

In practice, Foveon cameras have also tended to offer lower effective resolution than competing Bayer-sensor cameras, even though Sigma marketed them by counting all three color-sensitive layers together as a much higher megapixel number.

So the issue wasn’t that Bayer was perfect; it was that Bayer sensors delivered a better overall tradeoff of resolution, workflow compatibility, and market appeal. Foveon remained available, but mostly through Sigma, which bought Foveon and focused on building complete cameras around the sensor rather than turning it into a mainstream industry standard.