Clearly, this is a diffrent sort of Lex Luthor, one who just likes watching the world burn, à la the Nolan Joker.
[imaginary harp effect]
2010
Zack Snyder: Now that Nolan's done, can I make the next Batman movie?
Pleeeeeeeaaaase?!
WB: No, we need a new Superman movie now, because we want a cinematic universe, and Batman can't be the center of the because he doesn't have powers. So, make us a Superman movie.
Zack Snyder: Well, okay, but only if I can make it as dark and depressing as a Batman movie!
WB: Fine, fine, whatever.
2013
Zack Snyder: Now that
Man of Steel has made money, and we've agreed to put Batman in the next one, can I make Joker the villain?
Pleeeeeeeaaaase?!
WB: No, we need him to sell our Suicide Squad movie, plus he doesn't have powers, so he's not formidable enough to take both of those two on. So, make Lex Luthor the villain.
Zack Snyder: Well, okay, but only if I can make him as unhinged, weird, and chaotic as Joker! And only if I can give Batman the opening sequence, and a lot more screen time and development overall! And only if I can kill Superman while I'm at it!
WB: Fine, fine, whatever.