The usual debrief goes like this: impressions were fine, CTR was low, probably the creative. Or maybe the audience was off. Or the timing. You get a list of possible reasons and no way to know which one actually killed the campaign.
That's not a diagnosis. That's a list of suspects with no conviction.
Campaign Autopsy works backwards from the result. What happened at each stage, what the numbers actually say, and which specific decision upstream caused the downstream failure. One clear answer you can act on.