Why was John D rockafeller called rober barrens?

John D. Rockefeller was referred to as a "robber baron" due to his business practices that were seen as ruthless and exploitative. He gained control of the oil industry by employing tactics such as consolidation, aggressive competition, and price manipulation, which allowed him to amass significant wealth and power at the expense of others. This term reflects the negative perception of his business tactics during the Gilded Age.