There are a few reasons. I'll talk about two. One is technical in that Inmos had a signal processing business and was strongly staffed in that area. This offered the potential to eventually make a SoC solution that had CPU and MPEG in hardware. The other is that there were some smart people in marketing at Inmos who at some point decided that they would pick a small set of target applications that they expected to be growth areas, and where we had some existing experience, then devote serious dedicated resources to each of those areas. Two of the areas were STB and GPS. The serious resources devoted included engineers who would be pretty much full time available to the OEMs, and were dedicated to their target application. I think it was Richard Onyett who had the STB brief. He spent years working on those design in projects.

Also fwiw, Inmos people always considered the CPUs to be general purpose.