Forgive me for being a bit of a History noob but I always assumed that things would have played out pretty much as they have, maybe a few facts and figures off here and there but nothing that major in the grand scheme of things. But I always spent more time trying to figure out the mechanics of how time travel would work rather than paying attention in history class so pay no attention to me.
That is an interesting speculation: that things would be more or less the same.
It is particularly relevant given your interest in time travel, which this thread is, of a sort. Speculative time travel.
It also has important moral implications: reminding us that it took a lot more than one Adolph Hitler, no matter how brilliantly manipulative and lucky, for the Holocaust to occur.
It took enormous, deep-rooted anti-Semitism already existing for Hitler's insanity to root in. It took neighboring countries selling "its" Jewish population to Germany for slave labor and eventual extermination.
Still, Hitler's passion and strange fixation on the idea that Jews were genetically inferior, and that they were the source of mental retardation, was so strong, such an overall necessity for his vision of a pure State, safe from such genetic "corruption", that its hard to imagine an event on the scale of the Holocaust occuring without him, in the place and time in which he was.
It is an interesting condition of our existence: we are all a drop in the bucket, and yet, in the right places and times, any of us can have a profound effect on the World at large.
One never knows the ripples of causation one's actions puts forth into the world.