The main Qantas short-medium fleet is the B737. Have ~75 pax & 4 cargo aircraft. But QF have 28 off B330
Introducing a new brand-model has 10 of millions of $$$$ in set up costs, training, spares, etc before 1 passenger steps a aboard.
While many would not fly in a 737Max until after a few years when/if it gets in the air (including myself) QF has a long history with Boeing
https://www.planespotters.net/airline/Qantas