Remember that the big bubbles that popped in the last quarter century or so were based on the internet and housing, both very real and useful things that became a bubble because investors bet way too much speculating on them, including leveraging the rest of the economy for those bets.

Edit: Forgot my point, but even if AI is valuable for the future (which I'd agree with for AI in general but I'm still skeptical about LLMs getting there), it doesn't mean it can't currently be in a bubble.

Also, the dotcom bubble took out companies that were making real money doing real things right then because they started accepting IOUs instead of money, and did their own leveraging to the point where they couldn't afford to not get their IOUs paid back, which they weren't when the companies they got the IOUs from went under.

Nvidia seems to have about 50 billion in debt and 10 billion in cash. I didn't look at the breakdowns of when that debt is due, but it's possible the AI bubble might put them into bankruptcy, especially if their credit rating goes down and they have trouble refinancing.