Actually, Papaltine as Hitler isn't a great analogy, it mostly works as far as it does because both men wound up becoming dictators viewed as evil by future generations, or intended to be views so through the way the story was told. The scary thing about Hitler is that he was well loved by most of the global community despite how people deny it, he was incredibly charismatic and that was what brought him to power more than assassins. Indeed one of the big things about Hitler was his ability to actually convert many of his greatest rivals and adversaries to his side. This is the root of a lot of various conspiracy theories generally referred to under the umbrella of "Hitler's Magic Box". The bottom line is that when visiting a lot of his rivals Hitler showed a lot of them something that made them give up their rivalry with him and stand at his side. Hitler not only had an occult fixation, but some of the greatest historical and archaological minds of the time working for him, which is something else that Indiana Jones relied on. After World War II a lot of Hitler's records and such were destroyed or sealed at the same time a lot of Nazi scientists were being recruited. The bottom line is that great care was taken to ensure that nobody ever found out exactly what Hitler was telling or showing a lot of these people, many of whom were being contained and/or executed on the spot. As a result it's been a matter of speculation as to what was in the metaphorical box that apparently nobody was supposed to be able to make up their own mind about. Theories are of course rife, many suggesting Hitler's people had actually managed to connect all the dots between a lot of historical oddities. You have people like those who rant on "Ancient Aliens" suggesting he proved the existence of ancient astronauts or even communicated with them. Other theories say he actually found the remnants of Atlantis and thus was able to prove his racial theories beyond a doubt. See Hitler believed that the reason why Aryans were superior was because they were the most pure blooded descendants of the people of Atlantis, Atlantis having been once populated by psionic giants (in this case "Giant" meaning about 7' tall on average) who tended towards being blonde haired and blue eyed. When Atlantis sank the surviving Atlanteans bred into the human population, most specifically the people in and around Germany. A lot of his eugenic experiments and the work of guys like Mengela were intended to try and rebuild this "master race" through cross breeding those with the right traits. He was also heavily into psychic research in trying to unlock the powers of the ancient Atlanteans. A lot of that is more or less public record, and it also explains why he went off about the "Master Race" when he personally held none of the traits he was lionizing, the idea wasn't so much that the "Master Race" was anyone on the planet right now, but a race he wanted to breed back into existence... insane, but the point of "Magic Box" theory is what if he could actually prove all of this and some of the nuttier things he believed. Among other stories are things like how Hitler might have built a deepwater undersea city as part of a plan to excavate Atlantis once he had won the war. According to some stories various enemy officers as well as political rivals were brought there underwater as proof of Hitler's beliefs and it changed some of them. Of course no such thing was ever found, but I believe these old stories were sort of the inspiration for things like "Bioshock" (albeit people with a different philosophy building it), and of course "Iron Skies" which took the idea from an undersea base to a moon base.
The point of all of this rambling is that Hitler was an entirely different kind of leader from Papaltine, he did have rivals killed, he had his night of long knives, sure, but mostly he succeeded not because of that but because of his ability to convince people he was right and make them love him. What's more where Papaltine was involved in a personal power grab, Hitler arguably was not despite how it seems, since his entire "insanity" was based around him paving the way for the real intended leaders to re-appear, giving the earth to a master race he himself was knowingly not worthy of. Huge amounts of Nazi resources were dedicated to weird stuff that was in no way going to benefit Hitler, all those inhumane medical and genetic experiments, psychic research, etc... had another purpose and any benefit to the Reich was arguably secondary. If Hitler has been using all of his resources to fight the war things might have gone differently.
That said, I believe "Order 66" was based on the legend of the Knights Templar, where according to story the knights were so powerful and rich that it was believed they would be impossible to stop through conventional means as they would learn of any plot against them through their political contacts and put a quick end to it. So what happened was the leaders of the time who were threatened by the Templars sent their military commanders sealed orders only to be opened on a specific time and day, and not before. Inside was an order "kill the Templars" so in this way the order was distributed and a surprise attack became possible and the Knights Templar were wiped out. Allegedly this order took place on Friday the 13th which is why it's an unlucky day. I've read different historical versions of it, but I believe that was the basic inspiration for what happened to the Jedi, they died much like how a huge and powerful order of knights was brought down in reality.
That said I wouldn't be surprised if Papaltine took inspiration from a lot of historical dictators and tyrants, but I think comparing him to Hitler is like Apples and Oranges. Papaltine's charisma was of a different sort, and to be blunt I don't think he was bug nuts crazy enough by the standards of the world he was in. To be Hitler-like Papaltine would have to say be worshipping Space Cthulhu, planning on reviving a precursor race, or something else like that and have a gift for being able to turn the most invested skeptics into true believers in his cult of personality.