They boiled the frog on him. They had redundancy - two controllers, two phone lines, two collision warning systems.
They removed one controller. That was... not great, but it seemed okay.
They removed one collision warning system, for a short window. That was... not great, but it seemed okay.
They removed both phone lines. They didn't tell him. That wasn't okay, but he couldn't know that until he needed them.
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This also disregards that someone is always in the chair. Okay, let's say he quits. Then they're short an additional controller, making the situation worse, and someone else is still sitting in the chair when the exact same thing happens. "He voluntarily worked in an unsafe environment" is just a deflection from the responsibility of the people who have the authority and the opportunity not to make the system unsafe. His only agency was to quit his job or not, which wouldn't have any effect on the outcome.