I am actually somewhat convinced that s global namespace is one of the major factors of growth for Emacs. Yes, namespaces can be nice. But there is something about a playground that encourages all cards on the table.
And, notably, what makes elisp great is that that is largely the language that Emacs is implemented in. Even if you moved elisp to be hosted on the jvm, I shudder to think of having to do a ton of jvm inspired boilerplate to get a quick extension in.
Isn't that a point of commonality with Lisp Machines? Not that I've used one, but from what I read, one of their great aspects is that every function of everything running in a Lisp OS was available for impromptu runtime modification. IOW, you could modify anything even while it's running, without the need to rebuild it and restart it like we do now.
Having a global namespace makes the hot-reloading easier by not having to figure out in what namespace the redefinition should be happening.
That feature is pretty much only widely available in Emacs, now.
It certainly sounds magical. And the few times I work with bugs in Emacs libraries, it is amazing to jump to source so effectively.
But nothing beats the fun of writing a few functions to improve my beloved editor. If it was Java I just would not do it...
I am not taking away from it's accomplishments. But, in the domain of editors, it has netbeans, eclipse, and intellij as examples. Which are all impressive in their own ways, but a culture of modifications is not included in that list. :)