It is not easy to find the right fit as people are people and not machines. There are emotions and drama that becomes the variables that do not fit in well to the equation. Just because you can do the job does not mean you are the right fit. And then there are others who may a a good fit for months or years but not forever. People change and situations change. That is all part of the big machine we call the employment industry. But it spills over into personal lives and personal relationships as well.
I think this is why it is so important to have a growth mindset culture, where best intentions are assumed. Workplaces can get "toxic" these days as people seem to be more emotional than ever.