> I wonder though if Erlang might have been a footnote in programming history if it weren't for the mindshare that OTP generated.
It absolutely would be. There's plenty of "simple FP languages" out there. OTP is very definitely the main selling point of Erlang, and nowadays of Elixir as well.
I wonder though if Erlang might have been a footnote in programming history if it weren't for the mindshare that OTP generated. "Simple functional language" is attractive, but "simple functional language with world-class platform" turned out to be a game-changer.