Weather situations are time dependant, ie time heals all. I guarantee the fog in MIA lifted sometime later that day, if fact the longer you wait the closer you are to the fog from lifting. To land with fixed reserve plus 30 minutes after busting the minima smacks of being able to tell the future. 30 minutes of holding may well have seen the fog dissipate, qantas could not have possibly have known this when they busted the minima.
I say again with absolute certainty.... Embarrassing