On the subject of Martian Manhunter, he wasn't in a lot of Earth-3 scenes as they were Superman-Batman ones with the Crime Syndicate. J'onn correctly realized given President Wilson's daughter, Rose, that someone might target her to try to demoralize him. (This was shown when Rose and J'onn mild-melded briefly and we saw that her Mom had been killed by Ultraman's heat vision.) Needless to say, his foiling the Red Archer's plans and then driving him into the arms of the police with enough psychotrauma to get them to take him before J'onn did worse to him showed when Supes and Bats couldn't be there, J'onn could.
On the subject of Martian Manhunter, he wasn't in a lot of Earth-3 scenes as they were Superman-Batman ones with the Crime Syndicate. J'onn correctly realized given President Wilson's daughter, Rose, that someone might target her to try to demoralize him. (This was shown when Rose and J'onn mild-melded briefly and we saw that her Mom had been killed by Ultraman's heat vision.) Needless to say, his foiling the Red Archer's plans and then driving him into the arms of the police with enough psychotrauma to get them to take him before J'onn did worse to him showed when Supes and Bats couldn't be there, J'onn could.