Postacoglu plays the game, he's a bit of a character, gives them the soundbites and click baity headlines they need. The results are going his way at the moment too which gives them another narrative to push, alongside the "life after Kane" angle.
Emery is a bit of a nerd (respectfully) who says the same thing every time he's asked a question. He's not marketable, he's not talking about the Fonz or doing sweary rants at his teams that go viral. He was poorly treated by the media last time he was in England, and he doesn't seem to be someone who naturally would want that attention anyway. As a manager he's amazing, providing weekly content for the 24 hour news feed, not so much.
People inside the football world are always more aware of what's going on than we might give them credit for. Come January we'll have had Emery for over a year, be halfway through our first full season with him, be challenging at the top end of the table, and still be in Europe (hopefully!) Any targets we have will be aware, or be made aware, of what we're doing, and they won't need MOTD or any other pundits to be doing that job for them.
