How so? Memory bandwidth and capacity has been steadily increasing. On desktop for example, 10 years ago an i7-5960X was the absolute top of the line and it had a limit of 64GB, with most motherboards in practice being limited to 32-48GB, and this was an unthinkable amount of RAM at the time for desktop. Now the top end desktop chips support 192-256GB, and a year ago (before the RAM price spike) you could realistically buy that much if you wanted for a reasonable price.

Doesn’t seem like it was coming at a high speed if it took decades to manifest.

Not sure I buy that? There's a hardware/process argument that DRAM scaling is hitting a wall (for largely the same reason that logic scaling is, even though the fabs are different).

But DRAM has always been almost completely dominated by consumer device needs, and consumer requirements leveled off hard maybe a decade ago. Once you had a 4G system, things were mostly OK. Pervasive VM use and general bloat pushed that up by maybe a factor of two or three since, but that's it.

AI is different. It wants that capacity for different reasons and puts it in different places. And almost none of us really saw that coming more than ~18 months ago or so. Certainly not to the extend that you'd conclude "we've been ignoring it".