Byatt v Tolstoy: what makes for great historical fiction?

Assuming Tolstoy is a model for A.S. Byatt in her vast novel "The Children's Book," a comparison is revealing and not flattering to Byatt. Okay, give her credit for huge ambition. She's trying to encompass the "sweep" of history in this very long book, particularly as experienced by the artistic-radical-intellectual group of Fabians/Bohemians, not sure what to call them. But in TCB, unlike War and Peace, history is a background, a tapestry, and the characters don't really engage with the forces of their time. For example, chapter I read last night, suddenly takes on a new character - Hedda, actually not "new" as she was a pesky child in a few earlier scenes but we know virtually nothing about her - now she's introduced as a young adult and she's interested in the suffrage movement. Well and good - Byatt uses this an occasion to give an account of some of the key dramatic events in the movement in Britain: an attack on Parliament, a protest march in the rain and sleet, attacks by the police, heckling at speeches and rallies. I was not aware of this, glad to have read it, great material for novel I suppose - but not this novel, as Hedda is not a character to us but just a word on a page, and she does not engage with these events, we don't see them through her eyes, from her point of view, they don't shape her or change her - unlike all the great scenes in W&P, as Pierre walks through the cinders of burning Moscow, as he witnesses the battle at Kosovo (?), as he watches an execution - he feels these moments of history, and so do we, and we understand historical forces in a new way. Good historical fiction does not use history as a "setting."