How is John D Rockefeller and Andrew Carnegie similar?

Andrew Carnegie and John D. Rockefeller were both very rich men and, if they were alive today, they would be the two richest men in the entire world. They both owned major companies that monopolized their respective industries and crushed all competition. They were both philanthropists too and they both used railroads to keep their prices low.

They were both very successful in something. They each had a monopoly in something (Andrew was steel and Rockefeller was oil).