Nvidia designs most of the advanced chips that power artificial intelligence, and that has made it an earnings machine, producing astonishing profits that have buoyed the entire stock market.

In the last year, Nvidia shares have returned nearly 150 percent, helping to fuel the nearly 25 percent gain in the S&P 500 stock index. Yet, starting in late August, as the bedazzling aura surrounding Nvidia ebbed, the market stumbled.

“The magic spell has broken,” Aswath Damodaran, a New York University finance professor, said in an interview. For a year or so, he said, Nvidia could have reported virtually anything at all “and investors and traders would have found a way to convert that into good news.”

What changed? Nvidia hasn’t faltered. Its latest earnings report was awesome. Of all the companies associated with A.I., Nvidia has reaped the most benefits. Giants like Meta (Facebook), Alphabet (Google), Microsoft, Amazon and Oracle are voracious buyers of Nvidia’s technology.

The problem seems to be that, like a child who has eaten too many extravagant sundaes, the stock market didn’t find Nvidia’s latest rich offering of profits to be quite as phenomenal as it had come to expect.

For investors, the crucial questions concern the future: How big will A.I., the generational tech wonder, ultimately become and what will Nvidia’s stake in it be? Most crucially, how much is Nvidia, perhaps the core A.I. stock, really worth? The answers are significant for the entire market, where A.I. and Nvidia rival the presidential election and the Federal Reserve’s rate-cutting plans in importance.