Peru’s new president Pedro Castillo, 51, deserves credit for vowing to focus his government on improving the lives of the country’s poverty-stricken indigenous population. But his first steps in office raise fears that he will scare away investors, generate capital flight and — after a short-lived populist fiesta — create more poverty. Castillo, a leftist former elementary school teacher who had never before held public office, assumed the presidency on July 28 after winning the runoff elections with a razor-thin 0.3 percent of the vote. He controls only 37 seats in the 130-member Congress. Some hoped that Castillo’s minority in...