Why do you think so many Lisp fans (e.g., Norvig) went on to use Python instead of those ML alternatives?
Lisp did only do b) to some extent. It was and still is common to develop languages as internal or external domain specific languages on top of Lisp. ML was such an example. Often these languages then are/were ported away from Lisp to a specialized (and possibly smaller/more efficient) implementation. Thus Lisp served as a prototyping environment.