While it's true that both python and js are interpreted languages, making them highly portable, JS at that time was a very lightweight language with a robust runtime offered by mozjs, that was built to be easy to embed into other systems, while python was designed for being the framework in which you build apps directly, hence requiring deeper dependencies.
İf it works good enough for my laptop phone and pc then it's good enough for everyone else
Besides, it wouldn't have made much of a massive difference if it was lua or js, but even lua has it's issues leading to people preferring other versions of lua