The PLEO (Political Leaders and Elected Officials) delegates group broadly into pro and anti-Clinton, DLC, factions but they also split into numerous sub-groups.

Each Congressional district has its own layers of squabbles concerns within each state party with, again, its own concerns.  Elected officials have to maintain their power base within the party as well as listening, however badly, to the voters within their district.  They also have to listen to the Political Leaders within their district and state as these are the ones who run the GOTV, financing, and other activities needed to win elections.

While we are focused on the national ramifications, the PELO delegates are more interested in these local power relationships, struggles and issues.  

Further, the closer the Pledged delegate count the more important the PLEO delegates become.  Thus, the more they can get for their support on the first ballot.

It's a dance.