Gazumped
**** it wouldn't really matter what they had on board if it isn't sufficient to get them somewhere else. What do you do, hld or make approaches down to the minima until you're into a fuel emergency situation with the viz deteriorating or make a decision to go below the min while you may still get visual?
By the sounds of it the fog was in the early stages of forming, waiting longer may have put them further in the ****. I can't see an argument against the QF crews decision on that.
IMO, unless the ETAs were very close best for who could commence the approach first so as not to waste time while the viz is going downhill.