Hayek’s thesis in The Road to Serfdom is that one intervention inevitably leads to another. The unintended consequences of each market intervention are economic distortions, which generate further interventions to correct them. That interventionist dynamic leads society down the road to serfdom.
In perhaps the best chapter of The Road to Serfdom, Hayek details “Why the Worst Get on Top” in totalitarian societies. The chapter begins with a quotation from Lord Acton: “Power tends to corrupt, and absolute power corrupts absolutely.” Hayek then elaborates the Actonian insight.