So glad you wrote this response, Mark. As I'm reading through all of these comments (late to the party!), they were the thoughts resonating in my head.

People voluntarily rally around one of three things, personalities, actions or thoughts. Regardless of what the rallying point is, the effect is the same. Those who most effectively reflect, articulate or represent whatever people are rallying around become de facto leaders, whether they were intending to or not.

Rosa Parks wasn't seeking to change the course of history. She took a stand against indignity. She wasn't intending to become a leader, but was thrust into that position by the people who valued her action.