Markets tumbled at the start of the week as investors grappled with a mounting trade showdown and further turbulence in Tesla’s stock. The S&P 500 fell around 0.8%, stepping off its recent high, while the Nasdaq and Dow each slipped nearly 0.9% . It was a sharp reminder that market optimism can vanish in an instant when geopolitics and headline news collide. At the heart of Monday’s selloff was a resurgence of U.S. trade tensions. President Trump announced via letter and social media that tariffs of 25 percent on Japanese and South Korean imports would be implemented on August 1 unless new agreements were reached . Several other nations could face duties of up to 40 percent . Asian markets barely blinked—with Tokyo and Seoul even gaining—in response, a sign of investor skepticism that the tariffs would materialize or significantly impact trade . However, Wall Street wasn’t so sanguine. The Trump tariff threat, amplified by renewed jitters about inflation and rate policy, t...