I have wondered about that, too.

There's a note in my book about JA's History:

instead of arranging a conventional Whig narrative, which interpreted English history as a gradual march towards increased liberty and as a progressive defeat of absolutism, JA sets up history as pro-Stuart tragedy by placing the execution of Charles I as its climax and conclusion. As Christopher Kent writs, JA 'brashly inverts the Whig view of history' ('Learning History with, and from, Jane Austen', in Jane Austen's Beginnings, 64). [Oxford World's Classics edition]