We don't typically create new Topics unless there are already 20+ Featured Hubs that belong in the new category. I'm not able to find at least 20 Hubs on Shazam! or Captain Marvel. The reason behind this is that categories don't get a Topic Page until they have 20 Featured Hubs, meaning the Topic listed above the Hub's title won't be clickable. It's inconsistent and not a great reader experience.
If you do end up writing a ton of Hubs on each character, feel free to email me and I'll make new Topics for both at that point.