To a certain extent I can understand forgetting to turn on the pitot heat (who didn't miss an item in his career?), but a plane like this doesn't it have a clearly visible lighted annunciation of that situation? No "all indicator lights out before T/O" philosophy?
But let's face it, we have been taught, trained to the limit, brainwashed, programmed to always trust Your instruments. Now suddenly You AND Yr mate, amidst solid IMC, need to step back and use other sources/procedures to guide Yr plane.
Of course I also flew through sim sessions in which You knew this event was going to be "played". Easy stuff. But I was happy that I never had to tackle a situation as happened here, even if it was because of their own (?) omission.
Unlike an explosive engine failure, this one slowly creeps upon You, which makes is even more deadlier.