This has become one of the major themes of Sci Fi Time Travel Movies.
“What if I could go back in time and prevent...?”
First off, Hitler was evil, but the “what ifs”...
First off, would Germany still have started WWII? I would think probably. The hard restrictions that they were put under after WWI was ripe for some leader to push back against. Maybe it would have been a better leader and Germany would have won?
Without Germany and WWII - would the Soviets have at some point over-run Europe instead? (I have NO idea what their history was like at the time)
Without Hitler and the Holocaust, would the Jews have gotten their homeland back? Some day of course if one believes the Bible and they are destined for that land, but how much later?
Of course there are always a lot of “what ifs”.
What if Hitler had been killed in WWI to what if Hitler hadn’t been sleeping when the D-Day attack occurred. (If that story is correct).