In 2014, after the Obama administration and Cuba’s government announced an agreement to restore diplomatic ties, the world descended on Havana. Everyone from the Rolling Stones to would-be investors rushed to claim a stake in the island’s future. Raúl Castro, the long-serving minister of defense, had assumed power from his ailing elder brother Fidel several years earlier and launched moderate economic reforms: allowing for more small private businesses, loosening rules for foreign investments,