"One Man Caused One of Britain’s Most Avoidable Rail Disasters..."

No, YouTube headline. Unless you mean the person responsible for the system that allowed one person to be in a position to cause a rail disaster. And that's probably a small group holding that responsibility.

If the system allows a single person to cause a catastrophe then that is a system issue. And the responsibility lies with those responsible for the system. Blaming the immediate individual working in the system is convenient for those responsible for it, but not for those of us who'd like better systems.