You may have noticed that after his 2018 directorial debut with “A Star is Born,” Bradley Cooper fell off the radar for a while. Aside from voicing Rocket Raccoon in “Avengers Endgame,” making a brief cameo in “Licorice Pizza,” and producing “Joker,” Cooper didn’t return to acting until Guillermo del Toro’s “Nightmare Alley,” and the actor had one reason for taking on the role.