I think it's a mix. You don't have the holocaust without Hilter, but you don't have Hitler without the post war anger in Germany. The fascist movement predated Hitler's involvement and he would have gotten nowhere without them.

Within the GFFA, Palpatine took advantage of the legitimate anger against the Republic and their Jedi agents in order to start the Clone Wars. He didn't create the massive power imbalances and corruption, he just used them.