Which group benefited the most from railroad pools and monopolies?

the person or company that owns them

Business giants, or major businesses, and their owner (s) most benefitted from railroad pools and monopolies.

Railroad pools were the association of multiple railroad companies, who were essentially competing with one another, coming together to divide their traffic and large income generations.

Monopolies were lone sellers of a good or service who faced no competition givin them the ability to control the market, especially with extremely high costs for buyers, making their business rich.