WW2 was a consequence of WW1, which ended in injustice following US involvement, and created an environment where rabid nationalists like Hitler could claim to offer a solution. Hitler was bad, but his existence didn't arise out of nowhere. Further, there is no way his fascist economy could have fueled a long-term war, much less led to "everyone speaking German." The first half of the 20th century is clouded by propaganda and patriotic bullshit too.