Back then there weren't really ML libraries to speak of, you had to write your own. Though Symbolics did have a neural network tool and framework they sold.

And you could certainly do things like shuffle lots of data easily for more hardcore processing. For example, Symbolics didn't just have a Weitek floating point accelerator option for their systems, they had vector processing boards for them too that you could use from Lisp. (And even a GPU, the Framethrower, that did full-frame HD with 2D and 3D acceleration! S-Graphics is amazing for the time.)

Also, a lot of AI work back then was focused on symbolic processing. That's largely been eclipsed by the more math-heavy approaches these days but symbolic processing is still around, for example in tools like Cyc.