I feel like this is the opposite lesson than you should learn. Firing people sucks for everyone involved, but investing a lot of time trying to interpret tea leaves to determine if candidates are a good fit doesn't have a return-on-investment in finding better candidates and firing people less often. Instead it always makes sense to take more chances, support new employees, and use some mechanism like a probationary period to exit those who won't thrive before it's too painful.
I feel like this is the opposite lesson than you should learn. Firing people sucks for everyone involved, but investing a lot of time trying to interpret tea leaves to determine if candidates are a good fit doesn't have a return-on-investment in finding better candidates and firing people less often. Instead it always makes sense to take more chances, support new employees, and use some mechanism like a probationary period to exit those who won't thrive before it's too painful.