How did US-Iran ceasefire boost US markets but impact oil shares?

US stock markets jumped sharply after a US-Iran ceasefire eased fears of a wider war and signalled the reopening of the Strait of Hormuz. The Dow Jones Industrial Average rose 3%, while the S&P 500 and Nasdaq Composite gained over 2.5%. Airline stocks surged on lower fuel costs, but oil firms like ExxonMobil fell as crude prices dropped sharply.