Maxwell Lord is a government agent who can create illusions that are so convincing, they are indistinguishable from reality. He used his abilities on Superman so he believed he was fighting Darkseid when, in reality, he was attacking Batman. Since Darkseid is one of the strongest beings in the universe, Superman unleashed all his power on Bats. If it wasn't for Amazonian technology to heal Batman's body, he would have been a dead man. When Wonder Woman realised Lord would continue to brainwash Superman to commit atrocities, she snapped Lord's neck, killing him.
Although Wonder Woman had nothing but good intentions when she ended Lord's life, it made Batman snap. After Superman nearly killed him and Wonder Woman committed murder, Batman realised that he could no longer trust his teammates and so, decided he couldn't work with them anymore.
Shortly after, the Justice League Watchtower was blown up by a mysterious assailant. Due to Batman's distrust with the Justice League, Green Arrow accused him of blowing up the Watchtower. Disgusted that his former ally would accuse him of such a thing, Batman's resentment towards his teammates was cemented even further.
James Egan is on YouTube under Comic Kong with new videos every week. He has written 15 books about comics
1000 Facts about Superheroes Vol. 1-3
1000 Facts about Supervillains Vol. 1-3
1000 Facts about Comic Book Characters Vol. 1-3
1000 Facts about Comic Books Vol. 1-3
1000 Facts about Superhero Movies Vol. 1-3
Twitter - @jameswzegan85