Sometimes the plane was airworthy. Sometimes the pilot was competent. Sometimes the weather simply killed them.
DZ10 exists because intellectual honesty requires it. The framework's position — that corporate failure is almost always traceable to human decisions and structural vulnerabilities — is not the same as saying external forces never matter. They do. Regulatory acts, sovereign interventions, systemic market collapses, genuine black swans — these can destroy businesses that were structurally sound and well-led. The framework acknowledges this. It just demands very high evidential standards before accepting it.
The zone may only be assigned as primary when no other zone scores above 4. If any structural amplifier can be evidenced — a concentration that made the impact catastrophic, a dependency that should have been hedged, a cost structure that left no resilience — DZ10 is secondary at most. The test is both stringent and necessary: most companies that claim external force as their primary cause of death are wrong. The external force triggered the collapse. The structure made it terminal.