For one, all madara wanted from the start is to cast infinite Tsukuyomi.
http://www.mangapanda.com/naruto/625/16
For two, even if he defeated Hashirama, he knew that no one would side with him.
http://www.mangapanda.com/naruto/625/17
http://www.mangapanda.com/naruto/625/18
Here, proves that...