> And what about Lisp is enduser friendly?

It's not, it's developer-friendly. A basic Lisp interpreter is like a few hundred lines of code, so it's a very tempting system to embed. I think Lua is similar, but I haven't messed with it.

It's also powerful enough that most things aren't incredibly awkward to specify in it. YAML/JSON/TOML/etc have issues expressing repetitive things that can be solved in a for-loop/map in Lisp.

I don't even think Lisp should be an IQ filter. I wouldn't call myself a great or even good Lisp programmer, but the prefix syntax and s-expr's aren't all that hard to pick up. I don't think it's any more difficult than JSON, although it is far less common.

A fully bracketed prefix notation is unambiguous. It requires no knowledge of precedence rules. Small children can learn it. Your editor can indent it in a consistent way, no matter how you break it into multiple lines. You're almost never left wondering what element of the program is a child of what other element. You know the argument position of everything; there is no guesswork. If you misplace a parenthesis, the wrong indentation clues you in. Working with Lisp syntax requires few brain cycles; therefore, the syntax per se doesn't demand high intelligence.

If you can fog a mirror, you can probably edit Lisp.

> ultra-high-IQ people

I think that's much more stereotype than reality. People see all these parentheses and think that it must be a difficult language that requires a big mindset shift, like these purely functional languages with dependent types. In reality, it takes a week or two, plus an editor plugin that highlights matching parentheses, to get used to writing (function arg-one arg-two) instead of function(arg_one, arg_two). After that, it's smooth sailing. Just another decently designed language that's dynamically but strongly typed. Feels like writing Python, except with a bit of metaprogramming from time to time.

I think you're overestimating the importance of syntax and underestimating semantics. It doesn't take a very long program to get bitten by bad semantics. A few years ago, I was writing a game extension in Lua. It was only a couple hundred lines, and I still wasted hours debugging problems that would've been one minute fixes in Python or Lisp. All because of Lua's ridiculous idea of conflating arrays with hashtables, plus its habit of returning nil instead of raising an error when you do something that doesn't make sense.