Comment by josefx

> Netscape decided to add a programming language to Navigator. They pursued two routes to achieve this:

And the reason for that two language approach is given in the linked source:

> We aimed to provide a “glue language” for the Web designers and part time programmers who were building Web content from components such as images, plugins, and Java applets. We saw Java as the “component language” used by higher-priced programmers, where the glue programmers—the Web page designers—would assemble components and automate their interactions using [a scripting language].

Earlier sources clearly state that Java was intended as the primary language and JavaScript merely acting as glue.