When CAMM was announced, they (Dell) mentioned that one of the reasons for soldered RAM was due to electrical tolerances not being met anymore with regular DIMMs at the speeds they were reaching. CAMM was designed to avoid this, and ensures that each trace has the same length so there aren’t timing issues.
I’m no expert but it sounds plausible to me. From a manufacturing perspective, it makes sense that they’d want modular RAM so they can configure them at point of sale instead of having to manufacture multiple motherboards with only RAM sizes being different.
The 13 mini sold poorly because all of those same influencers just would not stop complaining that it had less battery life than a Max. I mean, of course the battery life wasn’t as good, because it was a smaller battery! But the people who want a mini aren’t influencers who need a phone that can go 18 hours without a break.
It was absolutely this manufactured “range anxiety” that killed it.