If Germany won an early victory, say by 1942*, would the Holocaust still have happened? Because there were other plans I believe (from both the Nazis and the Allied nations) for the resettlement of the Jews in places like Madagascar, Uganda, Alaska, Siberia and even Manchuria (Fugu plan) and Mindanao in the Philippines. The militant Zionist group Lehi even offered to help the Nazis fight the Allies in exchange for Nazi cooperation in the immigration of European Jews to Palestine.
Of all these plans, the Madagascar Plan seemed the most viable to the Nazis and the reason it was discarded was because of the continued war, the Nazis had no passage to the island and without the help of the British, transporting the Jews to Madagascar was logistically impossible. Now if the Germans managed to secure British help in transporting the Jews to Madagascar, I believe it would have been succesful. There would have been no immediate need for the Nazis to have resorted to industrial genocide in the form of gas chambers.
Now what world would result with a victorious Nazi Germany but without the Holocaust? How will the Nazis deal with the Slavic populations without the idea of gas chambers? Would they go with the original idea (according to the Generalplan Ost) of deporting them to the Far East? But that would only mean supplying the rump USSR with manpower resources for a future resurgence. And what would happen to the Gypsies in this TL? And would the idea of gas chamber-based industrial genocide still emerge in Nazi Germany? Was it inevitable hat something like that would happen?
*They secure peace with Britain. Barbarossa is launched earlier in April and Moscow falls by the end of '41, Stalingrad follows in the next year, leading to Germany taking the Caucasus. The Red Army surrenders at this point and the USSR is reduced to a rump state in its Siberian territories.