Why were monasteries common targets for early Viking raids?

Monasteries were common targets for early Viking raids primarily because they were isolated, undefended, and typically contained significant material wealth.1

As religious centers, these sites often held precious liturgical objects, and many had grown in power and wealth through royal gifts and land grants. Because they lacked military protection, they were easy targets for the short, hit-and-run tactics employed by early Viking raiders.1

Beyond the material gain, these attacks were often viewed by contemporaries as acts of profound desecration. For example, the 793 raid on the monastery at Lindisfarne—a preeminent center of Christianity—was particularly shocking because it struck at the heart of Anglo-Saxon religious life. While the violence and theft were devastating, the psychological impact of a pagan people attacking a sanctuary that was expected to have divine protection created a lasting sense of crisis throughout Christendom.1