What significant change took place in the 11th century that facilitated the rise of European Crusades to the Holy Land

Crusades, military expeditions, beginning in the late 11th century, that were organized by western European Christians in response to centuries of Muslim wars of expansion. Their objectives were to check the spread of Islam, to retake control of the Holy Land in the eastern Mediterranean, to conquer pagan areas, and to recapture formerly Christian territories; they were seen by many of their participants as a means of redemption and expiation for sins. Between 1095, when the First Crusade was launched, and 1291, when the Latin Christians were finally expelled from their kingdom in Syria, there were numerous expeditions to the Holy Land, to Spain, and even to the Baltic; the Crusades continued for several centuries after 1291. Crusading declined rapidly during the 16th century with the advent of the Protestant Reformation and the decline of papal authority.

a, both were musicians during the jazz age