5 whys usually leads to blaming someone which isn't useful
Sure someone made the change but it could've been anyone
consider asking “how did it make sense for someone to do what they did?”.
if an engineer appears to have made a mistake, look at the processes they used, the training they received, how frequently they interact with that part of the system or codebase, their workload, their oncall schedule and other relevant details that put an error into the broader context
Training exercises: responding to a controlled minor incident - like military exercises