Often I see this happen, and the result is the company loses out somehow. I think maybe metrics for “output” are wrong in many cases, and you’ve just canned someone who had a useful or even critical role you didn’t know about. A lot of people who are important to company operations are invisible!
Unfortunately that means that on paper, I have zero output while the people I help have all the output. Especially in computing/data science it's easy to fall into this trap; it takes a daily check-in to make sure that I'm working on the stuff that counts for me and my group.
Also accumulated know-how can be partially visible by writing out docs, patents, guides and the like. Definitely not enough but can increase visibility.