Why does everyone think Obito is Madara?

Question

Why does everyone think Obito is Madara?

Answer 1

I think Madara is dead because in Naruto Shippuden Sasuke ask his brother who is the another man witht he Sharingan then Itachi say it's Uchiha Madara but Sasuke again tell his brother that Madara should be long dead now, and Itachi say no Madara is alive. So, I think if Sasuke say Madara is dead then it may be Obito who has exactly like Madara's hair and maybe Obito will talk to Kakashi at the end when he is going to die and even Sasuke is going to die because he and Naruto fight each other coz Sasuke is going to destroy Konoha and at the end the whole Uchiha and Akatsuki clan is out.