Why couldn't Intel fab GPUs for Nvidia? Taiwan just had 2 7+ earthquakes this morning, so we can add that to the geopolitical risk of having a large number of the world's most advanced chip fabs on the island of Taiwan.
Other than process specifics, they could, and that's exactly what happened when the 1980s US Government got worried about a single CPU supplier. The result was (to some extent) modern cheap computing.