I mean, I get the concept of Dramatic Irony for storytelling purposes, but NONE of the characters noticed how controlling and abusive he was being? It wasn't exactly subtle

Such things are always easier to see from outside when we can look forwad in a narrative. In real life, and to characters in a story, you don't get every small aside, and have to weigh 'kind of an awkward dick' against 'probably an abusive asshole.' How much of your dislike is due to his sulky metagaming colouring your perception?

There's also a lot of social pressure to give yourself excuses. "It's not my problem", or "I'm sure they know about it and must be okay with it if they're putting up with them". We hear or see about abuse, and if it's not overt and violent, we tend to willfully ignore it.

It takes a lot of effort to speak up, sometimes.

I figure GM might be calling Rika or her parents or something.

Consider, most of them are actually primarily focused on the game, or at least things in that regard. Most of his conversations haven't likely happened aloud, where he's kind of a shit to her. As the OP said, nobody noticed because they're just focused on playing their people.