History's lessons are not about what happened (WWII happened) but about why they happened. But this is where the difficulty comes in. The “why” of things is not objectively knowable. Why did Japan attack Pearl Harbour? Were they greedy or was the US unreasonable and applying a racist double standard to expansion and empire? The answer to that is whatever “men agree to believe.”.
It is this agreeing to believe, the consensus that raises doubts in the validity of history. Napoleon famously quoted “History is a myth that men agree to believe.”
George Orwell also touched on this thought in his book 1984, “He who controls the present, controls the past. He who controls the past, controls the future.”