China's population density is skewed lower due to uninhabitable and sparsely inhabited mountains and deserts in Xinjiang and Tibet that make up about half the country. Without those regions China's population density doubles to around 300/km2.
True, mine is a generalization. However Italian geography also lead to heavy concentration of people in limited areas. Lombardy, the worst hit region, has a population density of 420/km2. Look at this map of Italian geography: https://en.wikipedia.org/wiki/Italy#/media/File:Italy_topogr...