Why was there a great migration in Ming Dynasty?

In order to strengthen military strength, the Ming Dynasty moved a large number of civilian households from Shanxi or mountainous areas to Juyongguan and south of Beiping. After Emperor Chengzu moved to Beijing in the Ming Dynasty, in order to make Beiping, the newly moved capital, prosperous as soon as possible, a large number of wealthy families and businessmen in the south of the Yangtze River were forcibly moved to Beiping, that is, for military protection and economic development.