I got to wonder that one because it’s something that Wehraboo like to say,even though it’s already being debunked (watch the potential history video on this one and I feel like history isn’t writte by the winner since loser can write it too (look at manstein/speer book per example)
It is an empty phrase, usually used to discredit any historical narrative without proper arguments. I had to think of the Potential History video upon reading your question (here: https://youtu.be/QPlxqADoVNE) because I think he does a great job in debunking the premise.
However, I think it’s a popular phrase thats applied to World War Two a lot since the opposing sides were so different - obviously a German perspective on History, would the Nazis have been victorious, would have been very different. I see the appeal of the The ‘Victors History’ argument though. The availability of sources is a legitimate concern. Churchill got to write his ‘History of World War Two’, Hitler didn’t. German War Criminals were tried and questioned at Nuremberg, Allied War Criminals were, if at all, not exposed as publicly. And many secretive (potentially criminal) operations or atrocities were exposed when the Nazis surrendered, as none was in power to keep them under the rug. But though the Allied countries, consisting mostly of democracies, should be transparent about operations and mishaps, we don’t know what has not been made public. It’s this idea that ‘they don’t want you to know the truth’ that gives a lot of ammunition to conspiracy theorists. Also, since the holocaust and nazi atrocities are considered war crimes and therefore ‘bad’, some people like to explain this as a subjective narrative of history reestablishing the ‘goodness’ of the ones who won.
So I get why people often go for the ‘Victors History’ argument, but don’t think it’s a valid argument in any case. It’s used out of desperation and ignorance and gives baseless fuel to baseless conspiracy theories.
I searched the word “victor” in r/shitwehraboosay https://www.reddit.com/r/ShitWehraboosSay/search?q=victor&restrict_sr=1 and my biggest problem with this line is how some will use to try to defend the nazi