Bank of America research points out that the current US stock market is characterized by the late stage of the Internet foam in 1999, and the concentration of the S&P 500 is high and the funds continue to chase a few AI winners. NVIDIA collaborates with Wall Street giants to plan a $500 billion AI infrastructure financing, raising concerns in the market about the alignment between capital expenditures and performance returns. Bank of America believes that when chip and cloud manufacturers, as well as large technology companies, become the core drivers of index growth, the surface prosperity of the market masks internal fragility. If AI revenue returns slower than capital expenditure expansion, index volatility will be amplified.