It’s not about assumptions on the hardware. It’s about the current demands for computation and expected growth of business needs. Since we have a couple years to measure against it should be extremely straightforward to predict. As such I have no reason to doubt the stated projections.
Networking gear was famously overbought. Enterprise hardware is tricky as there isn’t much of a resale market for this gear once all is said and done.
The only valid use case for all of this compute which could reasonably replace ai is btc mining. I’m uncertain if the increased mining capacity would harm the market or not.
BTC mining on GPUs haven't been profitable for a long time, it's mostly ASICs, GPUs can be used for some other altcoins which makes the potential market for used previous generation GPUs even smaller.
That assumes you can add compute in a vacuum. If your altcoin receives 10x compute then it becomes 10x more expensive to mine.
That only scales if the coin goes up in value due to the extra "interest". Which isn't impossible but there's a limit, and it's more often to happen to smaller coins.
Failure rates also go up. For AI inference it’s probably not too bad in most cases, just take the node offline and re-schedule the jobs to other nodes.