A very slow December was on the cards for most online sellers IMO, unless they were guaranteeing delivery or offered a pick-up option accessible at multiple outlets Australia-wide (like your big box retailers).

On my website, I had to post the last day to order for delivery in time for Christmas was the 10th of December (2 days earlier than Aus Post's published date of the 12th, which was a Saturday and impossible to post on that day here). Express was the 19th, also a Saturday, so I revised that to the 17th, but also advised that additional delays can and do still happen, so the earlier the order is placed, the better. People know through experiencing the last year that some packages will take a couple of weeks or more to arrive, and at the same time earlier this month there were restrictions being lifted in parts of Australia that allowed more shops etc to open than had been for a long time - IMHO it really is not surprising at all that at the time of year when there are time limits on when buyers are looking to receive their items by, super slow postage times nation-wide, and an opportunity to shop at B&M stores for the first time in ages, online sellers took a back seat to in-person retail for practically the first time this year.