been thinking a lot about "history" and "fantasy" these days. if you had to press me for The Thing that defines "the fantasy genre" it would be something like "the myths are true", since that is in itself a fantastical concept. myths, in the real world, are not "true", that's kind of the point
a bunch of tribesmen get together and build a few buildings and hundreds of years later the myth of the beginning of rome is that two lil babes were raised by a she-wolf. but if you went back, the lil babes would not be there! the myth grew out of the elements of the history.
but in fantasy, the myths are true, or at least some of them are, right -- the age of heroes was real, the lil babes did suckle at the teat of a she-wolf, the crow did steal the sun, whatever. the action of mythmaking is then recontextualized as history-telling, they become one-and-the-same.
IF YOU ASK ME, that's the core of what makes "fantasy" into "fantasy", because in the real world the history becomes all garbled in the telling over time until the emotional core remains but the details are usually lost or changed. i find both lenses fascinating (obviously) but realizing this little difference helped me whenever i'm doing idle fantasy worldbuilding or whatever