12- 13 century, why did the Germans start to immigrate to the Czech Republic on a large scale?

The Czech Republic's rich land resources and mineral deposits attracted the greedy eyes and ambitions of German feudal lords. 12- 13 century, Germans began to immigrate to the Czech Republic on a large scale. The first settlers were priests and monks. These priests and monks soon occupied the main position of Czech churches and monasteries, occupying almost half of Czech cultivated land. At the same time, in order to consolidate and expand its power, the church recruited a large number of knights from Germany to share the land and serve Czech farmers and immigrants from Germany. In order to increase the revenue of the national treasury, the Czech king also allowed a large number of German businessmen and craftsmen to enter the Czech Republic, and allowed the establishment of various autonomous cities with various privileges.