I tried to figure out what I thought the worst decision in human history was. I limited it to situations in which the decision maker(s) had information available to them to warn them, and the decision led directly to severe consequences, rather than being part of a chain of contingent events. Based on that criteria, I think the worst decision in human history was when the men advising President Hindenburg decided to make Adolph Hitler Chancellor of Germany. If they had read Mein Kampf, they should have realized that Hitler was an extremely dangerous man who shouldn’t have be allowed anywhere near the levers of power, but in their hubris they thought they could control him.