How can you found a movement you're already in?

Much of the reporting about Rosa Parks since her death has tracked the myth rather than the reality. For example, I've read in several places that her refusal to vacate her bus seat sparked the civil rights movement, or gave rise to, or led to the founding of, etc. etc. Ms. Parks was already active in the civil rights movement before her famous stand (sit) for bus equality. How can you found or give rise to a movement you're already part of? That her actions took the civil rights movement to another level, I readily concede.