Who are Mowen, Moore and Hooper (?) covering in this image? Someone (Hooper) obviously is covering FdP should he decide to go alone, but surely everyone should be sliding over 1 or 2 places? It almost appears that Mowen is signalling that (or maybe that is reading too much into this one still image).
Moore and Mowen were desperately sliding across, like the rest of the forwards.
The Boks smashed over the advantage line in the two preceding rucks, leaving the Wallabies defensive line broken. The ball was too quick for the forwards to pan out. If our forwards had done their job in the preceding ruck, then at least Horwill and Alexander could've had time to mark up correctly, will Moore filling in outside the pillar in this instance (between Hooper and Mowen).
Louw ran a great overs line and would've gotten around Alexander had he got the ball. Cooper misread due to Louw's line and took no-one by going for the intercept.
All in all, great play from the Boks. Cooper's misread made the try easy in the end, and yes, I think it was a mistake by Cooper, even if they would've scored anyway (which was pretty likely). Pretty much it's a mistake by Cooper as he took the wrong option, easy in hindsight I know.
However, that try was also set up by the demolition of our forward pack in the two preceding rucks, which just shouldn't happen. It wasn't the only time the Bok forwards did this to us. Off our restarts, we had them nicely on their 22 or just behind it, and they easily rumbled through us time and time again.