1. He was pretending to be Madara. Madara's name was fear enough to get his ideals going and stimulate this war.
2. That Zetsu that was on his body has a mind of it's own. Less efficient than him being in control of his own body.
3. This was likely a plot device that Kishimoto made to just give us readers interest. We saw Obito, and our curiosity after Kakashi Gaiden and seeing Tobi for the first time after Sasori died gave birth to a billion theories a week for about eight years. It kept us interested. Now we finally know it, and as mad as people got, they got more intense into this manga.
2. That Zetsu that was on his body has a mind of it's own. Less efficient than him being in control of his own body.
3. This was likely a plot device that Kishimoto made to just give us readers interest. We saw Obito, and our curiosity after Kakashi Gaiden and seeing Tobi for the first time after Sasori died gave birth to a billion theories a week for about eight years. It kept us interested. Now we finally know it, and as mad as people got, they got more intense into this manga.