I think it's important to note that while few people may have known about this today, this was generally common knowledge in the 1920s--based on a few google news searches I've done. In other words, it does not seem to be something the government tried to keep secret from the general population. (In fact, I remember my Dad telling me about this some 40 years ago!)
I'd imagine that the ones who drank the industrial alcohol were most likely victims of unscrupulous bootleggers.
This was a mistake (as was Prohibition in general) but it isn't as if the Government instituted a secret killing project. This was in the open and the denatured product was labeled as toxic (It still is). The real criminals were those who sold it as drinkable.