The starting assumption
At a job where I learned many valuable things, undoubtedly one of the most valuable things I learned is that it’s always best to assume that no matter what happened, everyone involved was competent and meant well.
You might find out that that assumption is wrong, but that’s not a conclusion you should reach lightly. It should come after investigation and thought.
That’s how I’d like to be treated when something goes wrong. But it’s also a simple acknowledgement of our shared humanity. In a bad situation people appreciate being treated like humans. They’ll remember when the tables are turned.