My assumption is one of a few things:
1. It became economically infeasible to continue builds of 8, 16, 24, 32, etc.
2. Apple discovered AI needs more than 8 GB of memory for future workflows
3. Apple will use RAM as a cutoff in 4-5 years… and NOT the chip
4. (Wishful thinking) Apple got tired of being made fun of in the tech press
It's quite economically feasible.
M4 iPad Pro comes with 8GB or 16GB. Consumers can choose between 256GB and 2TB storage. The RAM and NAND are picked by a robot arm.
Consumer sentiment and AI needs bumped up the base memory. We saw the same thing with dual external monitor support.