https://lithub.com/what-can-historical-fiction-accomplish-that-history-does-not/
Historical fiction is defined as movies and novels in which a story is made up but is set in the past and sometimes borrows true characteristics of the time period in which it is set
But for our own purposes, we need a better definition. Even the assertion that the story is “set in the past” is problematic, because we have yet to define what the past is, a potentially futile task given the possibility that the past—a past—may not even exist.
So let us agree, for now, that the past is that which is recognized by the present. The present sees the past, but the past does not see the present, because a past that saw a present would actually be a present seeing a future, which is—as far as definitions go—impossible.
The past—whatever it is—is good. The present is strange, and to be honest, there isn’t much of it.
Writing is the form that best mimics our experience of life
Why add a fiction book to the library of extant material? After all, are not historical accounts books?
The first has to deal with perceptions of truth.
Writers of fiction look for the bits that distort, and color, and qualify—that raise all sorts of questions where there were once answers. And all the other reasons to write historical fiction gather neatly here, where we tread into the more obvious: that historical fiction—like a spider at its web—thrives in the blank spaces between known and known, supplying plausible filler; that historical fiction tells stories through created personal perspectives; that historical fiction gives voice to previously underrepresented populations. These are powerful, worthy, interesting reasons to write novels and short stories inspired by historical subject matter, but perhaps not particularly curious.
So my first response as to why historical fiction is necessary is that material truth does not matter to the writer.
The other compelling reason to write historical fiction is its ability to perform. Fiction takes historical figures—significant or not—and turns them into actors
Historical fiction allows us to read about things that we know, but it also allows us to not know these same things. In this way, historical fiction most closely represents how the stuff of history happens. We write and read as we live, filled with possibility, and although we may progress to recognizable events, we—like the characters—do not know who we will be when we get there.