History isn't written by the victors. This is a common if pithy misunderstanding. For example, there has been explicit effort among historians over the last 40 years to give voice to previously silent actors throughout history. Examples include women, the poor, and the colonized.
I don't think it's a misunderstanding so much as a tautology. "Giving voice" is something victors decide to do on their own terms, they're still the ones writing history.
History professors come from a variety of backgrounds. Many of them are from groups that are still struggling in the US (ex. trans people). The definition of "victor" must become so amazingly broad that it becomes useless if you want to encompass modern historical narratives.