Katakuri chose to obey Big Mom rather than fight for his kingly ambitions. Say protecting his family is his kingly ambition. He does do it so he has basic CoC but in his heart of hearts he knows Big Mom is the greatest threat to his family and he has stayed silent about it. In order to unlock his AdCoC he would need to man up and confront Big Mom who due to hunger pangs or frustration is willing to kill even family members, those who Katakuri value and aims to protect. Perhaps his fight against Luffy showed him what must be done. Would be great if Big Mom manages to escape Wano, aims to go back to WCI but Katakuri threatens to kick her out if she doesn't obey his rule of her never ever touching a family member again. Fight, narrators box, winner: Katakuri (with AdCoC), king of WCI.