Apple acquired the team who made their in-house chips, PA Semi, back in 2008! Took quite a while to get good enough at it to go toe to toe with Intel and AMD. Even though they were able to license cores and designs.

[edit] Similarly, they acquired the modem business from Intel in 2019 (along with 2200 employees) so 'from scratch' may be a touch strong. [1]

[1] https://www.theverge.com/2019/7/25/8909671/apple-intel-5g-sm...