How bad this was depends on how "great" was framed. Hitler was a failed art student and low ranking infantryman who was let into the military (possibly by mistake) after failing his physical examination.

By 1939 (age 50), he had taken control of the German state and was soon after made a dictator by the Enabling Act, killed many of his political rivals openly in the Night of Long Knives, re-armed the German military after the treaty of Versailles totally gutted it, been given Austria, invaded the Sudetenland, kicked off the holocaust with Kristalnacht, signed the Molotov-Ribbentrop pact and occupied Poland - taking it in 3 weeks, and was at war with Britain/Australia/New Zealand (soon to be at war with everyone else).

"Great" doesn't necessarily mean "good" or "morally correct." Great can mean "person who has changed a lot of things" without making any moral judgment about that - think "great man of history" (not very materialist, I know). By that metric, obviously Hitler was "great" - even pre-WW2 and pre-Holocaust he had already radically changed global politics, had terrified much of Europe, radicalized a huge portion of the German people, and was set to potentially make a huge comeback from Germany's defeat in WW1.

Or they could just be a bunch of nazis over there at Princeton. That is also very possible.