They were not idiots in the medical sense but that they were ignoramuses is beyond doubt.
How could pilots be so ignorant to perform such a hazardous act ? IMHO, first: they have to be ignorant of aerodynamics and meteorology, second: gaps in their knowledge have to be filled by someone delivering his dead wrong message with great detail, patience and perseverance. Higher he be on the airline totem pole, it's easier for him to get the messages such as: "it will be blown off anyway" or "de-icing is useless but satisfies the authorities" across.
Unrealistic theory? Have a look at the last couple of pages on this thread.