Weber is writing in counterpoint to Karl Marx.  He believes that people and ideas count in history and that historical change is driven by more than just economics.

For Weber, the "prophet" is the primary agent of social change.  A prophet is a person with a "charisma," a magnetic personality, who comes to others  with the formula "it is written, but I say unto you" and who through persuasion brings about social change.  Ghandhi and Martin Luther King would be prophetic figures .  But prophetic figures can work evil in human societies, too, so we would have to include Hitler and Jim Jones, as well.

Now, Weber believes that two kinds of authority alternate in social movements and institutions -- charismatic authority and traditional/legal-rational authority.

What about relligion?  Religion is dying today.  He believes that traditional/legal-rational authority has so come to dominate industrial cultures through the ongoing processes of "bureaucratization" and "rationalization" that charismatic authority has effectively died out of modern culture. Religion cannot be renewed charismatically -- it cannont be made to fit modern times.  It no longer speaks to people and becomes fundamentally unpersuasive.  This is the effective death of religion, Weber believes.  A few people CAN still have a blind, unreasoning faith -- but this is a minority option, for how many can truly be satisfied with blind, unreasoning faith?

(Of course, Weber was wrong in predicting the death of charisma -- and religion.  But then he was writing all this just before the development of the radio, television and other electronic networks that bind us together today and which yield plenty of opportuniities for charismatic influence in human societies, for good and ill.)