You never can make all the right hiring decisions. References shade the truth, interviewers get sold a bill of goods, people end up being unethical, etc. it is what you do when you realize you have made a bad hire. It is tough canning someone who you have built a relationship with and might genuinely like, but isn't doing their job. That is why they say it is lonely at the top I guess. Apply equal standards across the board and most folks will understand why someone was let go, and the reasons are almost always self inflicted.
Now bs golden parachutes designed to protect incompetent millionaires, that is another story!
Go Gators