This is such an obvious move, that I predicted it 2 years ago: https://medium.com/@Jernfrost/in-3-years-apple-will-switch-f... My prediction in 2016, was that Apple would switch to ARM based laptops in 2019, so it looks like I am off by just 1 year. A quick summary of my argument back then was that ARM was getting fast ENOUGH, but are considerably cheaper. Standardizing on one CPU architecture for all their products…
In regards to audio applications like Logic and Ableton, single thread performance is probably the biggest factor. Individual plugins and effects are all single threaded within a DAW.