Someone who knows a lot of history is a history buff.

A historian works with (and may even seek out in musty rooms) primary and secondary sources to produce novel research and interpretation.

An AI is at best limited to ~reading sources that human historians/archivists/librarians have already identified and digitized.

Certainly value to be had here wrt to finding needles in and making sense of already-digitized historical records, but that's more like a research assistant.