As I recall, Matt Bishop and Dan Klein made significant contributions to research regarding bulk password cracking.

"Improving System Security via Proactive Password Checking" (1992) http://www.klein.com/dvk/publications/passwd-matt-final.pdf

Matt was the one who speed up DES cracking, and Dan Klein developed rules for cracking based on dictionaries. They should be acknowledged, IMHO.

One of the first things we did at school when we first saw the UNIX source code was to optimize DES to make a good password cracker (I remember the one used by the library was very badly written). It was then so easy to try /usr/dict/words on the then non-hidden password file.

crack was the standard of its day, could it have been that? (https://en.wikipedia.org/wiki/Crack_%28password_software%29)

No, we wrote our own. It's not hard.