most of muslims have to work with english speaking aussies if they want money they came here for a reason. so I'd say have vested interest in learning english. the parents of muslims, often dont speak english. Reason being they are only here to be part of the family and other than get dole payments they don't need english. 90% of their interactions are with other muslims etc
same with muftis, they only have to communicate with other muslims and 90% of muslims come from arab countries here. Other than know english for shopping and catching a bus, they dont have to learn english.
Basically, muftis are not here to be part of australia, they are here for muslims that are here.