The S&P 500 and the Nasdaq fell on Monday, dragged lower by declines in megacap technology names including Alphabet, while investors also assessed developments in U.S.-Iran negotiations. AI-driven optimism has supported Wall Street's recent rally, but analysts note that investors are increasingly questioning lofty spending by hyperscalers, who are raising funds to support infrastructure expansion. Alphabet tumbled 6.1 percent, while Meta, Amazon…