EGCS was eventually merged back into GCC (or rather it became the new GCC?). I don't pay attention recently, but XEmacs was/is pretty active along with Emacs.
I haven't seen any evidence in support of the original argument, though. Which open source projects have been killed explicitly by Big Tech that they didn't originally create? Microsoft spent ages trying to kill Linux but never succeeded.
LibreOffice is doing pretty well compared to OpenOffice:
* https://news.ycombinator.com/item?id=37645160
EGCS was eventually merged back into GCC (or rather it became the new GCC?). I don't pay attention recently, but XEmacs was/is pretty active along with Emacs.