Re mobile:
1. Timelines. Apple only transitioned to Intel in 2006 on their computer side, the first iPhone was announced in 2006. As a company they had little overall Intel experience. There was no "sticking with Intel" because they'd just switched to Intel concurrent with the development and release of the iPhone
2. iPod. Apple's prior mobile devices were already using ARM processors. That's a lot of experience and existing supply chain connections to take advantage of.
3. Mobile Intel chips sucked. They drew too much power and were not suitable at that time for a mobile device like a phone (already more power hungry with the wireless components compared to something like an iPod).