Without Hitler coming to power there would have been no WWII and no Holocaust.
In broad strokes there were four factors that brought Hitler to power.
The first factor was WWI, because without WWI there would have been no Treaty of Versailles. Kaiser Wilhelm went through life overcompensating because he was a forceps baby and the delivery stunted the development of his right arm. His family had him tortured as a child with no end of quack medical cures because he was heir to the throne and no monarch could be seen as physically imperfect. His life as an adult revolved around camouflaging his deformity, and he was spoiling for the war that would prove his virility. Willie is the uncaused first cause of Hitler.
Second, the Versailles Treaty was a serious kick in the crotch to the Germans. It was going to take them decades to dig out from under that debt, which significantly diminished their standard of living. And their national pride was grievously wounded by it. The rank and file largely felt they’d not lost the Great War in the first place but that they had been betrayed by their leaders, so many looked forward to WWI Part II.
Third, The Great Depression, which only magnified Germany’s financial woes from Versailles.
Fourth was post-WWI German politics, particularly the factious nature of Weimar politics and the fear of the rise of communism. Germany had more than 25 different political parties and they all were so small that only a coalition of quite a few of them could ever have enough collective votes to elect a Chancellor. The capitalist and anti-communist factions sided with Hitler because he was the one non-communist candidate who they saw as having enough popular support to overcome the powerful coalition the communists had formed. The general perception is that they didn’t think Hitler was the best candidate but they did think he had the best chance of staving off a communist takeover. But there are some who theorize that they believed a fiery national leader (such as Hitler) would reignite WWI, which was something they actively wanted.
Realistically, the only one of the four that Trump might have changed the outcome of was the treaty of Versailles. I can tell you Trump has studied Sun-Tzu because I see him repeatedly put his principles into action, such as always leave your enemy an honorable route of retreat. Which is a corollary to the (non-Sun-Tzu) principle of “the dying serpent bites deepest.” Trump’s implementation of this is that he wants everyone to walk away from the negotiating table with something to brag about, no matter how small. Just like the carnival barker says, everybody wins. Trump goes to the negotiating table not only with his own objectives in mind, he also considers how he will allow his opponent (trading partner) to “feel” he has won in some measure.
There was no “win” in Versailles for the German nation. Nothing but despair. Woodrow Wilson was one of the more moderate voices in the jury that would sentence Germany but we know from history (and hindsight is always 20-20) that Versailles was just too harsh for the German people to endure. Based on his past propensities, I’m confident Trump would have left the Germans some scrap to walk away with that they could claim as a victory, if only a moral one. Even if that meant he also would have to bribe or strongarm the most embittered of the Allied nations.
Might that have prevented the rise of Hitler? We’ll never know.
Why do people persist in thinking that WWII was only in Europe?
Japan had been rising for some sixty years at that point. WWII would have come if WWI had not been fought, if Hitler had not come to power if Europe had just continued to have petty little wars. War with Japan was always coming. And without Germany to ally with they would have allied with the USSR.
It would have arrived a bit later, probably in the 1950's but it would have come.
And considering their advanced in germ warfare it would have been a very nasty war.