As you already know the Man of Steel and the Dark Knight will hire an epic fight in Batman vs Superman: a Dawn of Justice. Now the big questions is who's gonna starts this fight, and why?
According to Badass Digest, Superman will start to annoy our favorite bat. But the Kryptonian was not up one morning and say: "Hey! What a beautiful day, I'll kick your, Batsy." So who's the manipulator who ordered the attack?
Say hello to the most determined bald guy in the DC Universe, Mr. Lex Luthor!!!
What Batman has discovered about Lex to push him to use Superman against him? How Lex can push Superman to do bad things, like to engage a fight against the Dark Knight (his future bff)?
To answer the first question, there are millions of reasons to that. A secret project to destroy something, or somewhere (as Luthor is fine to do). A billionaires conflict? Everything is possible. To respond at the second one, I only see two major reasons. First, maybe the Red-K aka the red kryptonite. Yeap! That one that removes any inhibitions of Superman. It can be cool to see the red kryptonite before the green one. Or maybe Lex keep Lois in hostage, or Martha Kent.
Oh wait! Maybe Lex is a "good" guy in this plot. Let me be clearer. Batman in this universe is just a myth, an urban legend. Lex discovers that the Dark Knight is real and maybe a threat, so he will use Sup' to fight this "bad" guy. At the same time Batman find who destroy hius satellite. At the end they'll becomes best friend, and call [Aquaman](movie:264237) to starting the Justice League.