In popular history, the narrative of the Second World War in Europe is pretty well defined at this point.
After the seizing power in Germany, Hitler annexed Austria and the Sudetenland, with Britain and France promising to come to Poland's aid should the Nazi's attempt to extend their conquest for lebensraum further east.
Then British PM Neville Chamberlain received assurances that Hitler was content with his territory as it stood, which obviously turned out to be insincere. (The Nazi's were liars, who knew?)
The Soviet Union then shocked everyone in 1939 by signing the Molotov-Ribbentrop Pact, guaranteeing peace between the two countries and carving up Poland between them, leading to British and French intervention and starting the Second World War in the process.
Eventually though, Hitler would betray his nonaggression agreement, launching Operation Barbarossa and invading the Soviet Union (Again, if you hadn't been following along: Nazis = bad guys) with ultimately disastrous results.
And this is generally where the alternate history timelines tend to diverge from real life. It's not uncommon for people, generally on the internet, to armchair quarterback one of the largest war machines in human history and explain how, with some changes, the Nazis could have emerged victorious.
But the truth is, that just isn't the case. Though the war certainly could've been prolonged had different decisions been made, with the sides as they were, there was no way that fascism would have eventually prevailed.