This Batman is the most literal interpretation of the Caped Crusader I've seen on the silver screen so far. He's on a crusade against Superman, and the only thing he has at this point is his conviction that he can leave a legacy for the world. His means are medieval, the branding of foes, how he's standing there as a dark knight in shining armour.
Everything he does in this film up until the fight is to make this crusade a success. He knows from the beginning the White Portuguese is delivering a weapon that can kill his enemy, that is revealed when Alfred starts calling him out on his lies.
It's no coincidence that the weapon he forges is a spear. A weapon that is extremely similar to the Holy Lance, the lance of Longinus, the spear of Destiny, the weapon that pierced the side of Jesus as he hung on the cross. And in this film Superman is helpless the moment Batman wants to stab him.
In this universe this character makes sense.