The answer is that each doubling of computing power adds roughly the same number of ELO rating points.

When you make a sound carry 10 times as much energy, it only sounds a bit louder.

If your unit of measure already compensates for huge leaps in underlying power, then you'll tend to ignore that the leaps in power are huge.

How you feel about a ram upgrade is one such measure, because you don't feel everything that happens inside your computer. You're measuring benefit by how it works today vs. yesterday, instead of what "it" is doing today vs. 20 years ago.

Can such a thing happen again? In particular, is it possible for AI to go foom the way humanity did?

If such lopsidedness were to repeat itself... well even then, the answer is probably no.

Isn't that lopsideness the state computers are currently in? So the first computer that gets the 'general intelligence' thing will have a huge advantage even before any fancy self-modification.