The first Emacs was written on top of TECO.

The came young students who had access to a brand new Lisp Machine in the MIT AI Lab (thanks to the welcoming spirit of Marvin Minsky and others). They implemented EINE (EINE is not Emacs) and ZWEI (ZWEI was EINE initially) and then Zmacs. -> Weinreb and McMahon. Bernard Greenberg wrote an Emacs in Maclisp for Multics. Hemlock was written in Spice Lisp. From then on a bunch of editors were written in Lisp.

Don't let you be discouraged. Learning to write well architectured programs is best done by writing programs.

I applaud those who put their thoughts between nested parentheses and turn them into working code...