What if Hitler was the best case scenario result of time traveler interference? He bungled a lot of decisions someone like Himmler probably wouldn't have. What if WWII is ultimately unavoidable, and every other timeline was way worse?
Maybe Hitler is actually a time traveller that pretends to be a nazi because from his timeline, the german fascist took over the world was way worse so he had to join the nazis to defeat the nazis? Maybe the Holocaust was like 10 times worse in his timeline and he intentionally did stupid decisions to reduce the kill count.
Germany was only 75 years old in 1941; for all we know it'd be some totally new country that ended up conquering everything. "Hail to Field Marshal Bing Bong Potatoman, ruler of our great glorious Zambonian Empire"