Lex Luthor (Jesse Eisenberg) is a master manipulator in Batman v Superman: Dawn of Justice, pulling all sorts of strings to coordinate the titular fight between Batman (Ben Affleck) and Superman (Henry Cavill), and he had Batman completely under his thumb the whole time. After seeing Superman damage Metropolis during Zod’s attack, Bruce Wayne went down a dark path, bent on destroying Superman, but little did he know he was merely doing Lex Luthor’s bidding all along.
Batman certainly had enough motivation to go after Superman, despite the urges of Alfred to back off, but the World’s Greatest Detective was so blinded by rage he didn’t realize he wasn’t uncovering a trail of clues, but breadcrumbs planted by Lex Luthor, who let him track K.G. Beast to his mansion, gave him the space he needed during a party to hack into his network to get his files on metahumans and Kryptonite, let him find the location of the Kryptonite shipment, and finally let him track the shipment back to LexCorp where he broke in and stole it for his own purposes.
