The butterfly effects would add up and and any zygote formed would not be the hitler-as-we-know anymore, since it would be a different combination of sperm and eggs.
Who needs guns when you got a time machine? Don’t like your highschool bully, just bump into their parents back in time. Or you know, “bump” ( ͡° ͜ʖ ͡°) into their parents.
For real, there was nothing particularly special about Hitler that made him the one and only being of his type.
It was a confluence of multiple differing things, the emergence of new media technologies, and the ability to repeat a single message over and over again to as many people as needed to hear them without any equally as loud voices of dissent.
Combine that with an incredible financial depression and the consequences of an ill thought war being foisted upon your country’s shoulders.
Admittedly, it was his own personal biases against the Jewish people that caused the Holocaust, and the Aktion T4 was similarly born out of his hatred of people with mental disabilities.
In any case, if you take a miserable nation, give them a lightning rod to direct all of the misery of their own lives at, and an eloquent or charismatic leader to tell them it is okay to vent their frustrations on the helpless people that surround them, then you too can create another Hitler.