If we look at Common Lisp, window managers are not new.
https://common-lisp.net/project/eclipse/
https://common-lisp.net/project/clfswm/
Well known is Stumpwm:
https://github.com/stumpwm/stumpwm/wiki
It's easy to write a minimal WM in Common Lisp:
http://paste.lisp.org/display/19072
http://donhopkins.com/home/archive/piemenu/uwm/fuwm-main.f
Robert Scheifler wrote an X10 server for the Lisp Machine.
http://ml.cddddr.org/slug/msg01083.html