Why were crusades called by the Pope? To convert people to Christianity
To regain control of Christian territories

Because By the end of the 11th century, the Holy Land—the area now commonly referred to as the Middle East—had become a point of conflict for European Christians. Since the 6th century, Christians frequently made pilgrimages to the birthplace of their religion, but when the Seljuk Turks took control of Jerusalem, Christians were barred from the Holy City. When the Turks then threatened to invade the Byzantine Empire and take Constantinople, Byzantine Emperor Alexius I made a special appeal to Urban for help. This was not the first appeal of its kind, but it came at an important time for Urban. Wanting to reinforce the power of the papacy, Urban seized the opportunity to unite Christian Europe under him as he fought to take back the Holy Land from the Turks