In the English Wikipedia about Gustav Vasa:
18th Century references in Britain
"In 1739, English playwright Henry Brooke wrote the play Gustavus Vasa, dealing with the liberation of Sweden from Danish rule. However, Robert Walpole, British Prime Minister at the time, believed that the play's villain was intended to represent him, and had the play banned - the first English play to be so banned under the Licensing Act 1737.
Later in the 18th Century, the name Gustavus Vasa was given to Olaudah Equiano, a prominent African ex-slave living in Britain and involved in the struggle to abolish slavery."
Gustavas was a fictional character based on Gustav Vasa.
Maybe you should research before trying to correct someone.