Yeah. Nah. Americans seem to have this warped idea that the Australian Open is really really important to Australia but it isn't. Yeah, it a big sporting event, and it has some tourist value, but it's of miniscule importance compared to thinks like our border security.
He flew down there with the understanding that his pre-arranged visa would be honored.
Not really. He either misunderstood the entry requirements (and to be fair, it looks like Tennis Australia may have given him misleading information) or he deliberately tried to bluff his way past Australian border law. Whichever is true, he only ever had a conditional Visa and it was conditional on him provided a valid exemption on arrival. He didn't have a valid exemption.
The Australians did not act in good faith so screw ‘em.
He also lied on his entry form. So arguing that the Australian government didn't act in good faith, but simply following Australian law as written seems odd to me.
Most Americans have never heard of the Australian Open before you made a big deal out of detaining a tennis player so it's a bit of a stretch to say that we have an idea that it's "really really important to Australia". We'd have to have heard of it to think that.
You detained a touring tennis player who has recovered from Covid and thus has better immunity than anyone with the shots, a guy that you'd previously given a visa to enter. Great Job!! That's quite a strong blow for border security, I'm sure the Chinese took one look at that and have decided to scratch you off their invasion list. That's about as much of a win for border security as our strip searching 90 year old Jewish grandmothers in wheel chairs after 9/11.
To put it bluntly, this makes your country look like a bunch cowering ninnies.