The goal was definitely to impede the other researcher's work, and I can imagine a few possible reasons for that. In descending order of probability, interpersonal conflict (in my experience, graduate students in the same lab tend to either become best friends or hate each other, with little in-between), trying to beat the other student to the punch w.r.t publication, or good ol' schizophrenic delusions that the person's work needs to be stopped (mid 20's is a pretty standard age for onset in men).

You can't logic your way out of a crazy box.

Trying to understand the root cause motivation of people with mental illness is usually futile and almost always fruitless

> This strategy doesn't make sense. What was the end goal? To have the other person keep buying new computers.

I would assume it was to interfere with the other student's research. That other person almost certainly had data on the destroyed computers that he either lost completely, or had to do extra work to recover when they failed.