There is no doubt that Germany and Japan had to be stopped. They were the greater evils of a slew of evils, and the most immediate threat to civil liberties in the war. Nevertheless, it's a horrific tragedy that the Japanese government, at least, was stopped in the way it was by so many innocent civilians killed by atomic fire.
However, Germany would not have been taken over by the Nazis had it not been subject to the economic upheavals that were imposed on it following World War 1 in the form of sanctions and the imposition of unreasonable debts. These didn't hurt the government nearly as much as the common people, and weakened the government of the Weimar Republic just enough to let an even more autocratic crew to rise in its place. In desperation, as always, the common people become vulnerable to the type of scapegoat-seeking and emotional manipulation into believing that a strong autocratic leader is going to save them by destroying all their "enemies," the latter of which is always presented as certain demographics--the Jews in that era; the Russians in the current one.
Of course, the real enemies were their government and the many other national governments whose sanctions on post-WW1 Germany brought the common people to that level of destitution. Hitler saw his opportunity, moved in, and the USA and UK found themselves having to clean up the mess of a horrific Frankenstein Monster their governments' actions had helped to create.
It was similar with Japan. The competition they were subjected to by the USA helped provoke their already awful leader into an act of mad desperation, and drove them into an alliance with Germany much as the USA is currently driving Russia and China into an unlikely alliance.
Regarding Russia back then: the USSR under Stalin was no better than Germany under Hitler. But Hitler saw Stalin as a rival and competitor, and monetary competition is the main thing that creates both enemies across the globe and very unexpected alliances that can quickly reverse themselves as soon as old rivalries end and new ones begin. Which is exactly what happened between the USA and the USSR with the onset of Cold War 1 (we're now in Cold War 2) following WW2.
So, yes, Nazi Germany and Imperial Japan had to be stopped, much as Putin needs to stop the shit he is doing now. But Germany and Japan would not have been taken over by complete fascists (as opposed to the proto-fascists running the Western nations) if not for the provocative actions of the USA, UK, and other nations that comprised the "good guys" during WW1. These problems stem from the type of competitive global world order we live under, not because some dictator decided to do something bad for the sake of being bad.