The countermeasures are "uses more RAM than is convenient". The ASIC counter-countermeasure was to add more RAM. The countermeasure was effective for 18 months.

So they steamrolled a bunch of cases, power supplies, and RAM? Kind of ironic.

Not PC cases and not PC power supplies, and probably not PC RAM. ASIC-based miners are built like embedded systems. None of these parts could be reused for general purpose computation.

You can see PC power supplies in the video.

You can see power supplies.

Monero has more extensive ASIC-countermeasures in place: https://github.com/tevador/RandomX

And FBA consensus "coins" don't need countermeasures because they dont need any kind of proof of waste lottery to make progress.

And neither does Paypal, et al. Why wouldn't I just use that if I don't care about decentralization?

FBA is BFT + decentralization. The F stands for "Federated" in contrast to "just" distributed system which are only physically decentral, federated system also decentralize the control. The key difference is that it does not need a puzzle (and therefore no resource wasting to solve it) to determine who will write the next block but rather BFT is used to agree on the next block. Its quite elegant compared to the puzzle and obviously way more efficient.

Protections in place which created a global shortage in GPU availability for machine learning and gaming, sounds like they didn't work great