I seem to vaguely recall there was a few years were Mozilla was shipping Python as an alternative to JavaScript. I want to say that HTML5 was what killed Python

I seem to vaguely recall there was a few years were Mozilla was shipping Python as an alternative to JavaScript. I want to say that HTML5 was what killed Python in Mozilla. HTML5 gained huge traction that Python never got. If someone remembers more clearly, please correct my cloudy memory.