C wasn't a one man band project (at least a two-man-band one at the start!) and neither was JavaScript. C also didn't have a formal specification for over 20 years (only an informal one) and JavaScript had a strong selection bias for interpreters that roughly conformed to the specification. But that didn't exactly help it, JS is/was notorious for differing implementations of browser APIs.

Each of them also has a strong need for a specification, as there are many differing compilers and interpreters. There are a few for Python but are specialized, the CPython interpreter is good enough for 90% of cases.