https://www.comicbookmovie.com/justice_league/geoff-johns-wanted-man-of-steel-to-have-a-lighter-tone-and-hired-joss-whedon-to-work-on-justice-league-a154169
"Geoff Johns and Diane were reading scripts, and Geoff Johns, to his credit, was concerned that there was not enough lightness or humor, given who the character is," one insider tells the site in regards to Man of Steel's production process and the way Johns was shut out. "Geoff definitely raised that point, but that current administration didn’t care that much about what Geoff Johns thought."That was then and this is now, though, and with Johns taking an active role in Justice League after the backlash aimed at Batman v Superman: Dawn of Justice and Suicide Squad, he and fellow DC Films boss Jon Berg decided that they needed to revamp parts of the movie. They wanted someone other than Zack Snyder to rewrite parts and add some new scenes and that was ultimately Joss Whedon.They were meeting with The Avengers helmer about Batgirl and soon realised he was the right man to steer Justice League in the direction they wanted. "Everyone was excited about Joss being a part of DC, and we thought he’d be great to write the [Justice League] scenes, the additional-photography scenes that we wanted to get." When a family tragedy led to Snyder's departure, he would take over as a director too and we're now all waiting to find out how Justice League turned out this November.