How did Nanjing become a haven for families fleeing northern China during the Eastern Jin dynasty?

During the Eastern Jin dynasty (317–420 CE), Nanjing—then known as Jiankang—became a haven for families fleeing northern China primarily because it served as the new capital for the Sima family court.12

Following the collapse of the Western Jin dynasty and the subsequent barbarian invasions that devastated northern capitals like Luoyang and Chang'an, many people sought refuge in the south. In 317, a prince of the Sima family established a government at Jiankang, providing a stable, albeit politically complex, center for those escaping the chaos of the north.21

As a result, a significant portion of the population in this southern kingdom consisted of these northern exiles. The city’s role as the seat of government and its relative security from the immediate reach of northern nomadic groups allowed it to function as a sanctuary, eventually fostering a period of notable cultural and intellectual development.21