Simplify the following text for a Grade 11 native English-speaking person.
Original: He was dubbed the `` King of Calypso '' â `` a title which he was very reluctant to accept ( according to the documentary Calypso Dreams ) â `` for popularizing the Caribbean musical style with an international audience in the 1950s .
Simplified: Some called him the `` King of Calypso , '' because he popularized this Caribbean musical style in the 1950s .