Now the popular portrayal of WWII seems kind of idealistic, but there's plenty of historical evidence to suggest many Allied troops really did not want to be there, and the scale of desertion [1] was quite high - In addition to corruption, mismanagement, and racketeering [2]. I only really considered this after encountering "Deserter: The Last Untold Story of the Second World War" by Charles Glass in a used bookstore…
The rest of the Allies always struck me more as cynical imperialists, and the whole narrative of the British desperately trying to stop that madman Hitler but Chamberlain loving peace too much to stop him as being a bit naive. Stalin saw things differently and saw the allies as trying to intentionally make Hitler stronger to keep the USSR in check. From that perspective, it's not shocking the allies went to war against the Nazis almost immediately after Molotov-Ribbentrop was signed. Plus you know, there were all the colonial shenanigans.
Also, with all that being stressed, it is actually unbelievable how comically supervillaniously evil the Nazis actually were. These were a group of people who made Josef Stalin seem ethical. It's hard to fight the Nazis and NOT be the good guys.