I think his point was not "why is Lisp not popular", but if it is so powerful, why has it not become more mainstream based upon that? If a language is truly as powerful as its advocates assert, should it need a marketing budget? Ruby, via Ruby on Rails, is famous, and has been used on lots of highly visible (successful?) projects, with no traditional marketing budget.

I think he's asking, if Lisp is so awesome, why doesn't someone ever do something awesome with it? It seems like a fair question.