What I don’t get is how can he possibly not know what she is doing?? It has gone on far too long now. People around him have to know. He just doesn’t care. Which seems insane.

By people around him, you mean Brad Davidson? The guy is a joke, a fraud, and a terrible manager/assistant/social media handler, whatever his job is. And I’m trying to stay polite.
David doesn’t seem to have anyone else around him for a few months, maybe years.
He said himself that he sees Gillian taking pictures and taping videos and he doesn’t think she’s going to post it on Twitter. I guess it’s okay if he doesn’t have this reflex, but every other celebrity, including Gillian, have someone to do this for them. And David has… Brad. So his life gets exposed by a post-teenager who likes to play his fans on Instagram, his manager mocks and disrespects his fans on Twitter by being 12 months late to deliver fans’ orders and he doesn’t even care to apologize, meanwhile, David is walking around, clueless about what freaking hell is happening because he doesn’t want to use his IPhone correctly.
This is infuriating and sad.