I believe the primary reason was tax-related, but the secondary reason is that there is already substantial personnel in the area who are experts in chip design and fabrication (Intel), with a strong pipeline for new talent from local universities for those skills.
Surprisingly, the area is also one of the largest Taiwanese communities in the U.S., which is a bonus for the engineers and their families who will be relocated from the "mothership".
Also, it's actually quite common for high-level Intel staff to fly back and forth from Portland and Phoenix. I am not sure if the same would be said about Taiwan and Arizona, but if they have staff in SV it wouldn't be too far-fetched.
Surprisingly, the area is also one of the largest Taiwanese communities in the U.S., which is a bonus for the engineers and their families who will be relocated from the "mothership".
Also, it's actually quite common for high-level Intel staff to fly back and forth from Portland and Phoenix. I am not sure if the same would be said about Taiwan and Arizona, but if they have staff in SV it wouldn't be too far-fetched.