They haven't made a final ruling on it. They're basically saying that it's so likely to be unconstitutional that they're temporarily prohibiting the state from enforcing it until they make their final ruling.
This is an injunction before the court case has taken place. They aren’t and can’t rule on a case before the case is heard. But it’s a very good sign that they issued this.
That said, they are definitely signaling to the Roberts Court that it is *obviously* unconstitutional and they would need to come up with extra special sophistry to decide otherwise.
You aren't wrong to be. The Sinister Six could still rule Florida's ban okay because Alito finds drag queens icky or something. Which is probably why they cited the "I know it when I see it" as obviously, hilariously wrong.
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This is the court saying "the government probably won't win, so the injunction can stay in place".
https://www.merriam-webster.com/dictionary/sophistry