Why should OSHA consider it the employer's fault if a crane operator lifts something that exceeds the crane's maximum permitted load when the foreman asks him to do so? The rated load capacity is posted right on the crane and the crane operator knows what it is.
It is the employer's fault because the foreman is part of supervision, so management is responsible for what he does. Management must see that all supervisory personnel who direct operation of cranes, and crane operators too, actually know the load limits. It is not enough to simply post them.