Since all history is interpretation, and all interpretation is by nature subjective (or biased), even historians don't always agree with each other on the causes, meanings, or realities of historical events. All one can say for certain is that at some point in history, this or that human wrote that this or that thing happened. Possibly there are records to prove an event happened. What events mean, or the realities surrounding events are interpretations. Even contemporary perspectives of characters and events are often colored by biased interpretation, and altered by things added or left out, or by the filters through which events and characters are viewed. Historians or historical writers can sometimes create the illusion of clarity while actually providing a very fuzzy picture, and the older the historical era or event the more this is true.
Into this fuzziness good historical fiction writers dive!