How did John Rockefeller contribute to the problems in the Gilded Age?

John D. Rockefeller contributed to the problems of the Gilded Age primarily through his monopolistic practices in the oil industry. By founding Standard Oil, he employed aggressive tactics such as predatory pricing and secret deals with railroads to eliminate competition, leading to a lack of market fairness and consumer choice. His immense wealth and influence also enabled him to wield significant power over politics and public policy, contributing to widespread corruption and the concentration of economic power in the hands of a few. This exacerbated social inequalities and fueled public discontent during the era.