Market Extra Why the S&P 500 was doomed to fall when Nvidia plunged after its earnings Investors worry about Big Tech valuations being inflated relative to what they’re actually worth, says strategist Nvidia Corp. has the heft to make or break the U.S. stock market — and on Thursday the technology giant dragged down the S&P 500. Despite Nvidia’s NVDA blowout earnings report Wednesday, shares of th...