One difference that strikes me with the .com bubble is that I don't remember the .com companies having sustained multi-billions losses / cash burn. They were not profitable but this is quite different. If (or when) the music stops, won't OpenAI go bust immediately? That's quite a counterparty risk those companies are taking.
Massive cash burn was an absolutely key feature of the dotcom boom/bust. Admittedly, it never really went away - there's always been a free->enshittification profit taking cycle since then. It's just the scale that's terrifyingly different this time.
OpenAI is ten years old, dotcom companies were 2-3 years old.
Some dotcom-boom companies that survived also had sustained multi billion dollar losses afair - Amazon and Uber for example.
They are counting on 'too big to fail'.
I believe we'd have to tease out what proportion of that cash burn is essential to keep serving compute to customers (which I assume to have profitable unit economics), versus what percentage is optional datacenter buildouts that could be paused in this situation.