Apple is in some respects a dinosaur. The way they ran that smartphone side of the business worked with there was growth in the area but as time goes on smartphones have matured to the point that if you bought one 2 years ago you can probably keep it 3-4 years before actually needing to upgrade and if you but a used one from a year ago or so it's good enough.@winb83 Apple being forced to lean back and production on iPhone X retirns after likely weak "XS" sales
Apple resumes iPhone X production in face of weak XS sales, report claims
From there the Chinese manufactures step in and make cheap lower end phones and mid range phones that are more than adequate.
Apple finds themselves raising their prices on their customer base that will continue to shrink as a result of the maturation of the market and the raised prices.
At some point and it might not be right now but something has to give or a death spiral is entered like what Cable TV faces. Apple is doing well now, maybe they transition away from smartphones leading the charge and something else becomes their bread and butter.