At a later date, Black Adam killed most of the Council of Eternity, leaving the Wizard as the only survivor.
However, this alliance came tumbling down with the rise of Black Adam.
Judging by those empty chairs, presumably a similar scenario happened in the DCEU.
But Aman’s uncle, Adam, was so consumed by anger and his need for vengeance that he stole Aman’s power (it’s strongly implied he killed his nephew) and became Black Adam so he could dish out his own brand of justice.