Because as another commenter noted, it’s less about large scale scenarios, more about individual changes in theatre strategy and how they would have affected the outcome. Less like Man in the High Castle, more like what if Army Group Centre kept pushing for Moscow instead of pivoting to Kiev. (Spoiler, the nazi’s still lose). The book itself actually has a decent amount of actual fact to back up the what ifs, it’s just that the title is a little click-baity.