It's probably not fair to put all the blame on the pilot...
Did the operator provide adequate training? Did the owner (you) do research before leasing out the aircraft to the operator? Does the operator have a history of ****ing engines? How does he instruct his line pilots to lean the engines? Have you asked them this?
I remember my GA days. The owner of the company insisted we run the EGT right before it would cut out to save $$$$ on fuel. Not his engines so he didn't care. Not that all the pilots did that....