The biggest motivator to move to Intel, as stated by Steve Jobs in 2005 (paraphrasing from what I remember), was that the power to performance ratio was bad on

The biggest motivator to move to Intel, as stated by Steve Jobs in 2005 (paraphrasing from what I remember), was that the power to performance ratio was bad on PowerPC. All the lead that PowerPC had had over Intel vanished. And given that IBM wasn’t interested in servicing Apple’s needs for consumer level chips (and Motorola, the other company in the PowerPC consortium, was struggling to scale up manufacturing), Apple’s pro machines like the PowerMac were struggling to keep up and improve. One PowerMac model with PowerPC G5 (IIRC) was even released with liquid cooling and had some customers complaining about leaks. The driver for the processor switch was actually Apple’s inability to get the right kind of chips it wanted on scale. As others have mentioned, the in-house design and the ability to get its chips manufactured for iPhones on a large scale triggered a big wave (of competitive advantage) for Apple. We’ll only see more of this as time passes.