[eru]

C started off as a single implementation, then a bunch of implementations, and only later the standard.

There's multiple implementations of Python, but you are right that CPython is the big one. Part of that dynamic is that CPython runs on nearly everything well enough (well, as good as Python runs), so that we don't really need multiple implementations. Unlike the first C Compilers.

Of course, Lisp is a family of languages these days. Scheme and Common Lisp have many implementations, but Racket or Arc only have one.