Don't Expect Fairness
Scenario One. Management has known for some time that the employee is incompetent or insufferable but has done nothing about it until now. A new and diligent supervisor may have decided to push for termination or the employee's infractions may have crossed some border of tolerance. Whatever the reason, the powers that be now want the employee's head on a pike. Unfortunately, the employee has a file filed with Meets Standards performance evaluations. Afraid that some plaintiff attorney will make this weasel out to be a victim and a credulous jury will agree, management winds up paying for a sizable severance package.
Scenario Two. The employee has been a good performer but the job has changed. Despite additional training and time, she is not able to pick up the pace. No other vacancies are available. Management will fire a very popular and genuinely decent person.
Scenario Three. The employee is a dangerous loon but management pretends otherwise because no one wants to be in the same room when Charles Manson gets the bad news. They'll keep transferring him from department to department in the hope that one day he'll win the lottery and go off to start a cult in the hills of Nevada. The latter never happens and the employee stays long enough to retire. Some terrified co-workers throw a farewell party for him in the break room.
Scenario Four. The employee is inept but charming and so is promoted. Once hired into a field in which a year or two must pass before incompetence can be clearly established, his career is off to the races. Promotions follows rapidly. Years later, management interns will ponder the amiable but empty suit seated at the boardroom table and wonder, "How on earth did that happen?"
Out of the above scenarios, note which person got the axe without a dime.