FNIDEQ, Morocco — It started with Instagram posts that suggested Spain’s border with Morocco was opening up. Then came Facebook users tracking coast guard patrols and TikTok videos showing where to swim. After many shares and comments, thousands of Moroccans became convinced that Europe was suddenly within reach. Within hours, young people began heading toward the border with the Spanish enclave of Ceuta in North Africa. Packed buses rolled into the neighboring Moroccan city of Fnideq. Regional trains filled up. Taxis did too. By the time authorities reacted, an estimated 60,000 people had reached Ceuta in just a few days, the largest migration surge between Morocco and Spain in years. More than 80 migrants died on both sides of the border, including some who drowned and others who were killed in a stampede, authorities said. Nearly all of the surviving migrants soon returned, but the fallout from last week’s events will linger. Rumors started online In the northern Moroccan city of Larache, about 93 miles (150 kilometers) from Ceuta, three friends watched a video posted by an Instag