UA had a larger network than VA/DL combined pre-COVID despite largely surviving on O&D on the OZ end.The only meaningful benefit I can come up with is that United's network into Oz is far better than DL, which is especially important now that VA has stopped flying longhaul.
On a related note, UA also accepted the approach from the Queensland Government (in partnership with BAC) with taxpayer funds partially funding the restoration of 'competition' on Queensland-USA flights post-COVID through the new BNE-SFO flights. Those will replace the now defunct VA long haul service.