You guys sound like a rabid lynch mob.
The simple reality is that engines fail and aircraft turn back all the time. This happens to all airlines - not only Qantas.
I suggest you are all going off half cocked. The fault in the engine may well turn out to be nothing to do with Qantas.
Will you come back here to retract the lunatic assertions if the fault is found to have been in the engine manufacture? Of course not.