The only reason big players become big players is by being good...

The only reason big players become big players is by being good at managing risk. If they do not manage risk, they could be out of business very quick. So in this case they are simply heavily exposed to AGO so they are selling down some of their holdings to manage risk. I would imagine they will keep a nice parcel to ride up into big profit in the coming year or two...or in the case where the IO price goes south again, at least they are not as heavily exposed to SP fluctuations as they were previously.

If I had a nice pile of AGO at 1c and it went up to 2.5c I would be selling along the way also.