Acquiring P.A. Semi got them Dan Dobberpuhl and Jim Keller, which laid a good design foundation. However, IMO, I'd lean towards these as the decisive factors to

Acquiring P.A. Semi got them Dan Dobberpuhl and Jim Keller, which laid a good design foundation. However, IMO, I'd lean towards these as the decisive factors today: 1) Apple's financial firepower allowing them to book out SOTA process nodes 2) Apple being less cost-sensitive in their designs vs. Qualcomm or Intel. Since Apple sells devices, they can justify 'expensive' decisions like massive caches that require significantly more die area.