Without their regular players, Australia looks really weak. Aiden Markram, Temba Bavuma and Matthew Breetzke took advantage of this, as all the Australian bowlers except Matthew Breetzke got punished by the Protean batsmen. Ironically, part-time bowler Travis Head was the most successful bowler for the Australians. Ben Dwarshuis and Nathan Ellis are very popular in various franchise T20 leagues. But I don't remember them performing consistently at the international level.
Exactly without their best players Australian team bowlers looked weak and South African batsmen especially Aiden Markram and Temba Bavuma and Matthew Breetzke took full advantage. It is telling that Travis Head like you said is not even full time bowler was their most successful player. This shows difference between playing in T20 leagues where bowlers like Ben Dwarshuis and Nathan Ellis are popular and much tougher world of international cricket.