Why was the Congo free state called the Congo free state at the close of the 19th century?

The Congo Free State was established in 1885 as a personal possession of King Leopold II of Belgium, who portrayed it as a philanthropic venture aimed at ending the slave trade and promoting civilization in the region. The term "free" in its name suggested that it was an independent entity, ostensibly free from colonial rule, and operated under a humanitarian guise. In reality, it was marked by severe exploitation and brutal treatment of the local population to extract rubber and other resources. The name was a facade for the oppressive regime that operated under Leopold's control until international outcry led to its annexation by Belgium in 1908.