Australia tried to redeem all of the questions raised about their form in last two ODIs in a single one. Even though they have already lost the series, they made a statement that they are not to be taken lightly. They had intention of making a good total as Travis Head and Mitchell Marsh completed their centuries in quick time but the largest contribution on reaching such record high score was from Cameron Green. Creating his personal best, he put 118 runs on the table in 55 balls. It was nearly impossible for South Africa to chase it and they struggled from the start. They were all out before playing half of the allocated balls and lost by a big margin of 276 runs.
Australia today scored 10th highest team total in ODI history. The target is huge but I am surprised to see batting of South Africa, the whole team got out for just 155 runs. You are right, though Australia already lost the series but their today's performance clearly sends a signal that they are not a weak team. Look at batting figures of Australia, only four batsmen scored 431 runs today. Three Australian batsmen were centurion while Alex Carey is the only one to score half century today.
If fortunately South Africa had already won the series, South Africa had been defeated by 276 runs today if Australia could have done the second match, then the results of the series would have changed. In today's match, the way Australia scored the 10th highest score with three batsman centuries shows that Australia made the mistake of decorating their squad. If they could have done today in the first and second matches, South Africa might not have won the series by defeating Australia. In today's match, Cooper Connolly has collected 5 wickets with just 22 runs in six overs, if he were to be the first and second team, then the Australia series would not have been lost.