(edit: not saying that was the case here, working on devrel usually makes it part of your job to publish code)
I would never fire an employee unilaterally, especially over something like this, when there's valuable IP at stake and you can just talk the person into agreeing to sign over whatever it is you need.
“I think the cause was that Workspace and certain leaders (and projects) were afraid of being disrupted.”
Suggests that there is much more to it. I suspect it’s actually about disregarding Google’s internal processes (which is forgivable) and then demanding to work unilaterally (unforgivable). The amount of positive feedback may have given the author too much confidence that he could dictate to leadership what comes next.
A Google Workspace CLI is a useful project idea but it isn’t groundbreaking, it’s something that the Google Workspace team should be involved in. I suspect he just wanted go steamroll over them. Shipping stuff in a team is never about just producing the code.