Dec 10 had SOS which was an ed-like line editor. And a port of qed IIRC. It had a concept of a viewport into a file with lines longer than 80 chars, other editors did folding but this one did scrolling in ascii. Emacs now does similar. Gosling Emacs was nice before gnu. Very simple cross file macro "do this sequence of commands" mode. Vi/ex used buffers and @execute to write programs the gosling Emacs was more "do it once then ask the editor to redo it again and again"
Nvi and Keith Bostic deserves telling too. Kind of died Midstream getting i8n and sub Windows fitted in.
The ed/sed/grep/awk unity over the syntax of the regex cannot be overstated. One investment in a syntax which embodied semantic intent in pattern match. The uplift into ex/vi was a no brainer.