Why did Madara pose as Tobi when with Deidara? I'm confused about when we first meet Tobi. He becomes Deidara's partner and acts helpless. If he was Madara all along, why did he have to go through the process of getting accepted into the Akatsuki?

Examples: when capturing the 3 tails and when fighting Sasuke
First of all


  Tobi is not Madara. He claims to be Madara, and everybody believes it, that's all. 


Tobi's true identity is:


   Obito Uchiha. He pretends to be Madara because he does not want to reveal his true identity because he should already be dead.


He keeps his goofball attitude so 


   that he can pretend to be someone else (Tobi),  but once everyone calls him Madara, he changes his attitude to serious.