Why are Rockefeller and Carnegie known as robber barons?

John D. Rockefeller and Andrew Carnegie are often labeled as "robber barons" because they amassed vast fortunes in the late 19th century through aggressive and often unethical business practices. Rockefeller dominated the oil industry with Standard Oil, using tactics like price-cutting and secret deals to eliminate competition. Carnegie, in the steel industry, employed similar strategies and was known for harsh labor practices, including the infamous Homestead Strike. Their immense wealth and influence raised concerns about monopolistic practices and the exploitation of workers, leading to the "robber baron" label.