I would say that the core reasons are well understood:
1) The fact that there is built-in syntactical stability in any Lisp since the code must comprise valid Lisp data structures + a couple of special symbols.
2) The second reason has to do with the fact that Lisp macros allow language extensions directly by users, provided those extensions comply with fact 1. When users can extend the programming language by adding libraries, there is little reason for the programming language designers to chase every trend in language design, ending up with the kitchen sink—sorry "multi-paradigm"—languages of today. The core stays small.
Lisps are built around being a simple base supporting in-language extensibility (it's the killer feature that has kept it alive as a language family, and there is lots of experience with how to do it in Lisp which means new Lisps tend to get it right from the start), which means that there is relatively little reason to break it to add features, you just build on top.
Of course, the downside of that is that it is very common for projects to have lots of code in what amounts to a project-specific DSL that is both close enough to be confused with and different enough for that confusion to be dangerous compared to how any other project does many of the same things.
The ecosystem also has a huge emphasis on backwards compatibility and finishing libraries rather than the constant churn you see in other ecosystems. I can usually find a 5 year old Clojure library and include in my project without any problems at all, and when a major library want to try out an idea that changes the interface, they usually start a new library instead of forcing everyone to use the new interface they've come up with.
I'd say if you're seeking simplicity in terms of environment and programming, Clojure is definitely the way to go. And this is coming from someone who knew 0% Java coding before jumping into Clojure, and almost never touch/read any Java code when doing Clojure programming.
IntelliJ + Cursive is not far behind. From the 2021 Clojure survey 43% of the devs were on Emacs and 31% on IntelliJ/Cursive. Then 12% VS Code etc.
Anyway I don't think an Emacs setup to develop in Clojure is that complex. I'm using Emacs with both Cider and LSP: doesn't strike me as particularly complicated to set up. If you're familiar at all with Emacs, it's pretty straightforward to configure.
If you're not familiar with Emacs, you can use IntelliJ with the Cursive plugin: apparently as much as one third of all the Clojure dev opt for that setup.
As a sidenote apparently 52% of the Clojure devs are on OS X and "only" 37% on Linux.
When you have a project source file open you can M-x `cider-jack-in` (or C-c C-x j j) to open a fresh repl right in emacs. I found this useful advice for after cider and clojure mode are installed (skip the “configuration” section) - https://www.braveclojure.com/basic-emacs/
Setup on the Clojure/filesystem/JVM side was just leiningen - install lein and then `lein new app foo` gives you a fresh project dir for `foo`. You should probably install lein before the emacs stuff as cider may need a working Clojure install, not sure.