The description of Mr. Rockefeller as ''robber baron'' is definitely a negative characterization. The reason why it is a negative characterization is that it insinuates that Mr. Rockefeller was a man of great power, and used its power to gain more wealth and even more power by stealing from the people bellow him in the hierarchy.
Now, the stealing part can be seen from two perspectives. The first one by using force, and taking the money or the possessions of the people. The second one being by stealing through making murky business and illegal things behind closed doors.
The Mayans natural resources was limestone, salt and volcanic rock, and were able to thrive in it despite unstable climates. They could grow corn, beans, squash, and cassava in the most harsh and difficult to live in environments