Blah. A lot of blame, some blame, or no blame doesn't really matter. The postmortem outcome will likely be the same anyway: here's a bunch of safeguards that need to be sorted out to prevent the thing from happening again. Whether it is done in breadth (looking for many hazards/safeguards) or depth (focusing on a few), there'll be a to-do list that needs to be actioned, and then -hopefully- actioned. And that's really all you need out of the process.