What were the historians doing before that? Making bread? I'm not sure why you would call them historians if they didn't study the past (or document the present, perhaps).
You reveal a very rationalist perspective ... or maybe you're just using "study" in a much looser sense than I'm taking it. The first person to hold the position of "historian" at a University was the Von Ranke I mentioned in my last post. Much of what you consider history is most likely very recent. Are you familiar with things like Romanticism?
As I mentioned, history can be about building a political identity, about establishing personal glory/honor, about entertainment, about transmitting moral lessons, about understanding the essence of other cultures. None of those things really involve "study" in an academic sense ... and I prefer the narrower definition of words to the broader definitions. Otherwise words become vague, meaningless, and part of a semantic whirlpool.
Further, for those considered to be the first historians (Greeks like Herodotus), history was considered a form of literature (an art) told about recent memory - stories from the historians lifetime. The idea of studying past documents, authenticating them, and writing history based upon them, didn't come along until the Renaissance.
Perhaps you can learn things from the past. Also truth for the sake of truth if worthwhile in my opinion.
Questions of truth, what constitutes humanity, what ideas work and what ideas don't work - those questions can also be part of history.
I don't think it's a hard science, but I do think it's about trying to figure out what really happened... as best we can.
That's part of it, don't get me wrong. But people seem to make it a larger part than it really is. It takes on the idea of minimalism and reads like some medieval chronicle (pretty dry if you've ever read chronicles or minimalist history):
1754 - Albany Plan on Union
Feb 1763 - French and Indian War Ends
1763 - Pontiac’s Rebellion
Apr 13, 1763 - George Grenville as Lord of the Treasury
Apr 5, 1764 - Sugar Act
1764 - Currency Act
...
Pretty boring ... and IMO pretty useless.
I don't see why that would lead to Hegel or Marx.
If history is a hard science, then the patterns of the past can be used to predict the future. Therefore Marx must be right in his theory of dialectical materialism, and so his prediction that the proletariat will rise up and seize the economic reigns from the bourgeoisie must be true ... remember, I said this was part of the age of positivism. People believed Marx had stumbled onto a scientific truth. I don't think many today appreciate the impact he had on his time. The aristocrats were shaking in their boots because the science of history had just proclaimed their doom.
If history is the science of humanity, then it must be able to determine through critical analysis which human factors lead to success and which lead to failure, and that means the race in which those factors dominate is destined to lead all other races.
If Hegel is right in the idea of thesis and antithesis producing a new synthesis, then ... anyway, on and on it goes.