What is the most significant impact of John D Rockefeller and why? What was the most important development during the Gilded Age? What is the rationale behind your answer?

John D. Rockefeller is remembered as among the most important businessmen of the so-called "Gilded Age." He was an oil tycoon who, through shrewd and ruthless practices, created a massive corporation called the Standard Oil Company that gained a near monopoly over the production, refining, and distribution of oil. He was thus an example, and a prime mover, in two of the most important developments of the period. These were the rapid development of industry and the rise of massive corporations. Rockefeller was among the business leaders who supplied the rapidly-expanding economy with one of its most important capital goods--oil. At the same time, his strategies for cornering the market in oil through forming a trust in which companies ceded control to a board of directors was emulated by leaders in many other industries. He exemplified the process of consolidation in big industries. He also exemplified the ruthless ethos of business leaders of the time, and was among the leaders in lobbying to avoid regulations on his business. For these reasons, Rockefeller was among the most important and powerful men of his time.
https://www.history.com/topics/early-20th-century-us/john-d-rockefeller