I always remember Joe Armstrong's quote (which is an adaptation of the of Greenspun's tenth rule):

“Any sufficiently complicated concurrent program in another language contains an ad hoc informally-specified bug-ridden slow implementation of half of Erlang.”

That is, while other languages and systems barely scratched the surface in terms of distributed programming, Erlang was perfecting all the models needed for it, because that's what it was built for. So everyone else is now playing catch-up with Erlang.