>"They are joined at the hip and co-ordinate their activities."<
You are a damn liar, and you know it.
History tells us that movements are composed of the various elements or groups within the movement. The groups within are always connected thru leadership. Sometimes overtly, sometimes covertly, sometimes as a matter of fact. Sometimes they are enemies. Even as enemies, they take cues from each other.
When movements expand, the number of groups in the movement expand. Most frequently the individuals forming the new groups comes from an existing group and are well trained by and heavily influenced by their former leaders. It always benefits them all to participate in a multi=level hierarchy. Doing this enhances their power witin the movement. It enhances their ability to set the agenda, to influence the direction of the movement.
Groups in a movement are also linked by membership. If you look at all the individuals in a movement you find an infinate number of opinions and attitudes. It is not uncommon for individuals to identify with two or more groups. Often the committment the individual wishes to make neccesitates multiple membership.
You need to understand that much of this is determined by human nature and how humans organize themselves.