given that GNU Emacs does not implement a file system, has no process scheduler, has no driver for Ethernet cards, doesn't have a driver for a framebuffer, ...

given that GNU Emacs does not implement a file system, has no process scheduler, has no driver for Ethernet cards, doesn't have a driver for a framebuffer, ... the screen would be dark and there would be no i/O... whereas the Lisp Machine is a computer with a stack-oriented CPU running a relatively capable OS written in Lisp only (incl. disk driver, file system, NFS, DNS, SMTP, FTP, TELNET, graphics, processes, postscript printer support, users/groups/networks/sites, editor, graphics editor, file browser, process browser, printer dialog, screen shots, mouse handling, tape backups, cdrom reader, ...).