Maybe because interest just isn't there? I've given WB shit for their marketing in the past but not here. There's only so much you can do to sell people a small scale action comedy
They were still part of the MCU. A brand renowned around the world. That automatically makes them more known that someone who occasionally showed up in 2 niche cartoons
Ant-Man and GOTG got 2 movies each and Captain Marvel got teased in one of the biggest movies ever. They're also part of the biggest movie franchise on the planet
Shazam showed up in 2 niche cartoons. And only in a handful of episodes at that
How is Shazam more known again?
Aquaman was tracking for 65m for weeks and that's about where it landed
The low numbers sound reasonable. He's an unknown character and not part of a popular brand