I think the safe bet is not that Ferrari suddenly can compete for wins now, but rather that RBR underperformed here due to a combination of factors.
First of all, lacking data from what Max would have done blurs the picture a lot. Second, RBR did a rare strategy blunder with Checo and had him try to protect his front tires too much in his first stint, which did not pay off at all and in fact backfired completely. It also sounds like they didn't get the setup right, which wouldn't have helped.
Lastly, Australia is notorious for teams suddenly performing much better or worse there out of nowhere, and for performance at Melbourne not being representative for performance anywhere else on the calendar. It's very possible Albert Park was a circuit that happened to suit Ferrari and not suit RBR at the same time.
It looks like just the perfect storm really, and I assume it's business as usual in Suzuka. Please let me be wrong, though!