I'm not 100% sure of the specifics, but Nintendo took a pretty different approach from Sony or Sega at this time. Sony and Sega both rolled their own graphics chips, and both of them made some compromises and strange choices in order to get to market more quickly.
Nintendo instead approached SGI, the most advanced graphics workstation and 3D modeling company in the world at the time, and formed a partnership to scale back their professional graphics hardware to a consumer price point.
Might be one of those instances where just getting something that works from scratch is relatively easy, but taking an existing solution and modifying it to fit a new use case is more difficult.
Nintendo instead approached SGI, the most advanced graphics workstation and 3D modeling company in the world at the time, and formed a partnership to scale back their professional graphics hardware to a consumer price point.
Might be one of those instances where just getting something that works from scratch is relatively easy, but taking an existing solution and modifying it to fit a new use case is more difficult.