Joseph Pulitzer was a Robber Baron because he used his wealth in a way that only benefited him, and had no regard for the people who were negatively affected by his actions.
For the answer to the question above,
Decrease in unionization. The Sunbelt was and is an area where unions are much weaker than in the old industrial areas. As people and jobs moved to the Sunbelt, unions grew weaker. I hope this helps