> People do learn, but it's a slow process and a lot of people can die in between.
I recently listened to a podcast about the death of President Garfield. He almost certainly would have survived the assassination if he had simply been left alone, but he was treated by a doctor who believed the writings of Dr Lister were utter nonsense that no right-thinking American would fall for and spent days probing for the bullet with unsanitized hands. This was many years after Lister had proved that washing hands saves lives.
And Garfield might have been a great president. At the very least, we know he wasn't power-hungry, because he endorsed a different candidate and even made a speech on the floor of the convention for the other candidate and continued to support that candidate after Garfield had been put forward, only finally acquiescing when he got a majority of the votes and the convention. Then in his early days in office showed himself to be a highly effective president. If only....