He saw what Marvel did with Iron Man and thought he could strong arm DC into doing that for him despite not knowing or understanding what exactly had to come together for Iron Man to go from B or C list hero to the franchise player during the MCU's zenith. Also Black Adam is the arch nemesis of a hero, you're skipping so much of the character's history and story by just having him show up randomly as an anti-hero. He should have swallowed his pride and provided a star making performance as a villainous Black Adam in one or both of those Shazam movies and used his political muscle to work his way in as the top heel in the DCEU before slowly becoming an anti-hero and getting his own film. Even if the DCEU collapsed like it did in this timeline, a killer performance as Black Adam, the arch nemesis of Shazam, could have given him enough leverage to be retained for the James Gunn reboot. Now his whole shyt is in limbo because he wanted to cut the line.