What is the consensus history thesis on WWII?
It is hard to say what “the” consensus historical thesis about WWII is. This is because there are many aspects to WWII. Because there are a variety of aspects, there are also a variety of consensus historical theses about WWII. In this answer, I will look at two consensus theses about the war.
One consensus thesis has to do with why the war happened in the first place. The consensus is that the Axis powers, mainly Germany and Japan, caused the war because they were unhappy with the status quo. They were unhappy with the way they had been treated after WWI and they wanted a bigger place in the international order. Because of this, they took aggressive actions that eventually caused the war to happen.
Another consensus thesis is that Germany lost the war because of the invasion of the Soviet Union. Hitler did not have to invade the Soviet Union. The two countries even had a non-aggression pact with one another. However, Hitler did invade because he felt Slavs were inferior to Germans and he wanted to take their land for use by Germans. He also felt sure that his military could defeat the Soviets easily. He was, however, wrong and the Eastern Front was a disaster for Germany. The great majority of German losses in personnel and materiel were suffered on the Russian Front. It is unlikely that the Allies could have defeated Germany if it had not been so badly weakened in the east.
Both of these represent historical consensus about the war, but there are other aspects of the war for which historical consensus exists. Please ask another question if you want to clarify what aspect of the war you are asking about.