CUPERTINO, July 30 -- On any other Tuesday, the number alone would have been the story. But when Apple Inc. AAPL briefly crossed $5 trillion in market value on July 29, the market was already busy destroying it elsewhere: the Dow Jones Industrial Average was falling 1,153 points, semiconductor stocks were unraveling, and investors were questioning whether the tens of billions being poured into artificial intelligence data centers would ever earn a return. That Apple floated above all of it, if only for an intraday hour, said more about where Wall Street thinks the AI economy is actually going than the figure itself.

Shares of Apple touched $342.89 during Tuesday's session, the price at which the company's outstanding shares briefly added...