You're right. A good postmortem/root cause analysis would START from "unwrap" and continue from there.
You might start with a basic timeline of what happened, then you'd start exploring: why did this change affect so many customers (this would be a line of questioning to find a potential root cause), why did it take so long to discover or recover (this might be multiple lines of questioning), etc.
You might start with a basic timeline of what happened, then you'd start exploring: why did this change affect so many customers (this would be a line of questioning to find a potential root cause), why did it take so long to discover or recover (this might be multiple lines of questioning), etc.