Presumably he got better in the intervening decades, but part of how we stopped the Morris Worm was that it was badly written (see the various version of With Microscope and Tweezers for detail, particularly about the "am I already running" check that ended up being why it got noticed, "because exponential growth".) Even for "bored 1st year grad student skipping lectures" it should have been better code :-)

(Also, writing a Scheme dialect was a first-semester CS problem set - if you're in a 1980s academic CS environment it was more effort to not accidentally write a lisp interpreter into something, something in the water supply...)