Still, the reason for choosing a language for whatever are always more social and path-dependent than technical (reason 1: initial developer of whatever really likes the language, reason 2: language is seen as hip within some crowd, reason 3 (later in the game): management feels language is safe). Technical reasons for choosing a language typically tend to be post-hoc rationalizations. (I mean, no sane person would choose Javascript for an editor based on technical reasons alone, yet here we are.)
[0] https://lem-project.github.io/ [1] https://www.lispworks.com/products/lispworks.html
You can think of Emacs as a kind of software Lisp machine with an emphasis on editing. Although that analogy only works well if you squint or if you don't know a lot about Lisp machines.
As someone who first learned Lisp through Emacs Lisp, I found it fun, well-documented, and powerful. Once you grok the basics of how the system is dynamically glued together, infinitely hackable, and self-documenting it's kind of mind-blowing.
purely for text editing? No. But that's not what distinguishes Emacs, it's famously very mediocre at it. The point of Emacs is to be a fully transparent, inspectable, dynamic and changeable environment. In spirit similar to Smalltalk systems like Pharo. And for that a Lisp is not the only choice but a very good one.
There's very few languages and environments that facilitate jumping into any place, making a change, compiling or evaluating a block of code or treating it as data and continuing seamlessly.
BTW emacs is written in C.