There are many different reasons. Firstly, Apple built experience over a decade designing and building the chips, taking over more and more of the design and IP

There are many different reasons. Firstly, Apple built experience over a decade designing and building the chips, taking over more and more of the design and IP. Then making these chips at a Intel competitor TSMC, who has a different business model to Intel. Apple were also willing to compromise. The first years had weird experiences for customers with Rosetta, broken apps and Macs that could only drive a single external monitor and connect to few devices. Yet we clearly saw the power efficiency from the better foundry tech at TSMC, coupled with decade of saving watts for mobile phone batteries.