Apple started acquiring companies with chip design expertise while Jobs was the CTO. The first processor that had some custom design by Apple was the A4 which was used in the 2010 first generation iPad and iPhone 4.
I can’t believe that Apple wasn’t working on the first 64 bit in house ARM chip by the time SJ resigned in 2011 that was introduced with the 5s in 2013.
Building the processor in house probably IS a good call. In Jobs' day, even he didn't build the processor. But nowadays, things are different.