Earlier quoted context omitted.
Mediatek is in the picture because NVIDIA outsourced everything in GB10 but the GPU to Mediatek. GB10 is two chiplets, and the larger one is from Mediatek. Yes, Mediatek uses off the shelf ARM CPU core IP, but they still had to make a lot of decisions about how to implement it: how many cores, what cluster and cache arrangements, none of which resemble NVIDIA's Grace CPU.
Thanks for the clarification. I was surprised to learn it is not a single chip; thought they did something akin to Apple Silicon integrating some ARM cores on their main chip. Kind of disappointing: they basically asked MediaTek to build a CPU with an NV-Link I/O.
From NVIDIA's perspective, they need an answer to the growing segment of SoCs with decent sized GPUs and unified memory; their existing solutions at the far end of a PCIe link with a small pool of their own memory just can't work for some important use cases, and providing GPU chiplets to be integrated into other SoCs is how they avoid losing ground in these markets without the expense of building their own full consumer hardware platform and going to war with all of Apple, Intel, AMD, Qualcomm.