Guile was designed as an extension language, which CL was not. So, that's one reason. Guile also has a something like 90% working implementation of an elisp com

Guile was designed as an extension language, which CL was not. So, that's one reason. Guile also has a something like 90% working implementation of an elisp compiler to guile bytecode, a JavaScript implementation and (I think, though may be wrong) a working Lua compiler. None of the other mentioned scheme implementations were designed for embedding, even if they are fine implementations themselves (which they are).