Traders are investigating the reasons behind the largest reversal of the S&P index since April.

Nvidia released a strong financial report, employment reports confirmed that the foundation of the U.S. economy remains solid, and Wal-Mart's quarterly update showed that consumer spending is still ongoing. Despite all the signs indicating that the U.S. stock market should have welcomed a "risk appetite warming" day, the optimistic mood in the trading hall did not last long. The S&P 500 index rose by as much as 1.9% within the first hour of opening, but by 1 pm, the increase was completely reversed, resulting in a 1.1% decrease - the largest index reversal since the market turmoil in April, with market capitalization evaporating by over $2 trillion. The volatility index broke through 28 points. There are various speculations in the market about the reasons for the reversal: some traders pointed out that the spending in the AI field is huge, but there are concerns whether the related revenue or profit is sufficient to support this investment; some believe that the bitcoin price falling below $87,000 for the first time since April is a contributing factor to the stock market crash; and some stock traders expressed concerns about the overvaluation of stocks, as well as the increasing market volatility as the U.S. options expiration date approaches.