Neowin published a story that a former Intel engineer cited quality control issues and frequent complaints of Intel's 2015 Skylake offerings as the primary reason for Apple's switch to ARM from Intel.

Former Intel engineer reasons that Intel's Skylake lineup led to Apple opting for ARM

Earlier this week at WWDC, Apple finally confirmed that it will be switching Macs from Intel to its custom ARM-based chips. The move had been rumored for a while but the conference was the first time we received official word from the firm. Apple's own silicon will bring with it some key advantages, including improved performance levels at lower power consumption and the promise of iPhone and iPad apps natively working on macOS.

Former Intel engineer reasons that Intel's Skylake lineup led to Apple opting for ARM