All good points
Ushuaia and
Trevor the lover . Perhaps the ops centre were rattled and whilst a 5 hour delay due to late departure might be able to be tolerated and pulled back slightly, a 10 hour delay meant there was no return from here and thus diverting the flight meant they could get the following flights back on time however there appears to be an 8 hour wait in Melbourne before it took off to Phuket for it's next trip so I am a bit stumped.
This aircraft had already completed a Mel-DPS-BRS-DPS-Mel trip on the 26th/27th so this looks like a very rash decision by Ops and were there not other crews on board being shuttled? Perhaps they thought that a lot of people could go home so reducing the hotel bill a bit. All conjecture on my behalf.