Causation implies an active role in the outcome, not just a passive connection. The investigation proved his actions were the causation of the collapse.
Pro Tip 2/3
Not Always Direct
Causation might be indirect, meaning it's part of a chain of causes, not the only one. The report suggested that poor maintenance was part of the causation for the system failure.
Pro Tip 3/3
Evidence-Based
Causation often requires proof, and isn't assumed just because two events are related. The scientists could not prove causation between the two phenomena.