That's why it's a union job
Also he's the first person to die on accident so it's that and the safety of everyone else
They do not 'need' to follow others, they just need to refuse unless all safe and green.
If they never start to drive it's the companies problem to deal with angry non-dead customers
Every train network has situations where drivers are authorised to proceed against a red signal. Not usually at full speed though.
At most face unlikely discipline.
Here they would even have valid reason to refuse - order was given for full speed, regulation says low speed ready to stop.
So a "No, i'm not doing that, you're moron" would be justified.
A written movement authority is a signal as well in railway terms. It's more like "I don't trust your second traffic light, that you placed next to the normal one, because the normal one is broken".