Lua's presence is honestly hugely because it is so easy to embed in other programs. If you needed some scripting capabilities, Lua was the way. Whether it's a webserver (nginx) or editor (vim) or a window manager (awesome), Lua was the easiest & best at hand option to integrate.
There is a huge opportunity, IMO, for more players here. Deno definitely has some good gestures toward a this. Wasm though seems like the likely general heir, and will have many different offerings for how to do that (Deno being one!).
> There is a huge opportunity, IMO, for more players here.
There are quite a few embeddable scripting languages [1]. I think these days it's less common to embed a language mostly because there are good high-level languages that applications can be predominantly written in.