Idiot got it right despite himself.
I think there is a definitional problem here in defining “a great leader”. Hitler, Lenin, Stalin, Mao, Ho Chi Minh, Pol Pot, Mussolini, etc. would all qualify as “great” leaders if you are looking at what they accomplished from scratch. But, and a very important “but” is trying to define how a megalomaniac, psychopathic genocidal murderer is “great” instead of “he was a great psychopath who got other psychopaths and “true believers” to follow him and do whatever he wanted.
Greatness should be defined by peaceful, creative, positive contributions to society, not by a body count and number of cities and towns destroyed.
However, the professor misspoke badly about “interviewing” someone of historical significance. He should have said that he was fascinated by how a psychopath could rise up so successfully and destroy half the world and tens of millions of people in this “modern age”, i.e. the 20th Century, and that he wanted to understand this phenomenon by interviewing the person who did it.