Grann paints a stark picture of the systematic exploitation faced by the Osage Nation. Despite their wealth, they were subjected to guardianship laws designed to control their finances, leaving them vulnerable to manipulation and violence from unscrupulous individuals seeking to seize their oil riches. The murders themselves were a brutal means to this end, with each death bringing the perpetrators closer to inheriting the victims' wealth.

The Osage murders serve as a pivotal turning point in the early history of the FBI. Tasked with investigating the crimes, a young J. Edgar Hoover saw an opportunity to prove the agency's worth. Grann reveals how Hoover, eager to shed the Bureau's reputation for incompetence, utilized innovative investigative techniques, including undercover agents and forensic accounting, laying the groundwork for the FBI's future.

At its core, "Killers of the Flower Moon" is a chilling testament to the destructive power of greed and racism. The book exposes the dark underbelly of the American Dream, where unchecked avarice, fueled by prejudice and disregard for human life, led to a calculated campaign of violence against an entire community.