a 2080S from 2019, a high end SKU, would struggle with many modern games at 1440p and higher. A profession streamer would be unlikely to use a 2080S.

On one hand a 2080s would still be good at doing what it was doing 6 years ago. If there are new needs, and unlimited power availability, then a new card in addition to whatever AI workload the 6 year old GPU can do in addition to the new card makes sense... if that card still works. Selling your 2080s or whatever old card, does mean a fairly steep loss compared to original price, but 6 year depreciation schedule is ok... IF the cards are still working 6 years later.

$3m NVL72 systems are a bit different, as one out of 72 cards burning out can screw up whole system, and datacenter power structure and expertise requirements, would have low resale value, though I assume the cards can be ripped out and sold individually.

They very much can be expected to engage in what is essentially accounting fraud.

Oracle this week "proudly boasted" that they get 30% margins on their datacenter, and stock went up. This is not enough, as it is just 30% over electricity costs. Maintenance/supervision, and gpu costs/rentals don't count, and it is unlikely that they are profitable, though it's not so much accounting fraud as it is accounting PR.