What I recall from Erlang writings and videos is that, basically, Ericsson's C++ developers didn't want their cheese moved and successfully deployed the obvious (and not obviously unreasonable) arguments about how C++ was the industry standard, as above. I think Armstrong also admitted that the Erlang crew had a bit of a cocky attitude and wasn't great at winning others over.
This reminds me a lot of Ron Garret's story of the difficulties of advocating for the use of Lisp against the industry standard C for space projects. Sounds like a lot of the exact same dynamics.
