Why does workplace mobbing happen?

I am struggling to understand the psychology behind people/coworkers who make it their lifetime mission to push a worker out the workplace for no reason whatsoever. Like this person is a hard worker with good work ethic and has done nothing wrong, yet certain people in the workplace sabotage that person and make it their mission to eliminate that person from the workplace for good. Usually it’s a group effort and it is done very insidiously

Why does this happen to hard workers? What motivates them to use tactics to push someone out the workplace?

Why does workplace mobbing happen?
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