> The fact that Apple released 3 phones in 3 years with this form factor shows me that it is a profitable market segment and that there is demand.

Correlation does not imply causation. Apple might also be releasing them to use their old manufactured parts, Apple has a very healthy recycle plan for users who trade in their phones, not all Android OEMs have that. And Apple likes to boast about how environmentally friendly they are. 2 of 3 phones you mentioned are using some older parts.

So the releasing could purely be reuse some old parts thus reducing the manufacturing costs, and gain a little higher profit on these despite having low sale numbers from these.