>> 1. Some guys sent a bunch [thousands] of weird and obsessive messages to a musician

One guy. Hundreds of messages, not thousands, from the decision (https://www.supremecourt.gov/opinions/22pdf/22-138_43j7.pdf):

"From 2014 to 2016, petitioner Billy Counterman sent hundreds of Facebook messages to C. W., a local singer and musician. The two had never met, and C. W. never responded. In fact, she repeatedly blocked Counterman. But each time, he created a new Facebook account and resumed his contacts. Some of his messages were utterly prosaic ("Good morning sweetheart"; "I am going to the store would you like anything?") - except that they were coming from a total stranger ... Others suggested that Counterman might be surveilling C. W. He asked "[w]as that you in the white Jeep?"; referenced "[a] fine display with your partner"; and noted "a couple [of] physical sightings." ... And most critically, a number expressed anger at C. W. and envisaged harm befalling her: "Fuck off permanently." ... "Staying in cyber life is going to kill you." ... "You’re not being good for human relations. Die."

>> 2. Musician never gets a restraining order

The decision says she contacted authorities, doesn't say whether she asked for one:

"She stopped walking alone, declined social engagements, and canceled some of her performances, though doing so caused her financial strain ... Eventually, C. W. decided that she had to contact the authorities."

>> 3. The law says the threats are based on intent, and no threat seems to have materialized

No, law says that the charge is based on emotional distress caused, no need for intent:

"Colorado charged Counterman under a statute making it unlawful to "[r]epeatedly . . . make[] any form of communication with another person" in "a manner that would cause a reasonable person to suffer serious emotional distress and does cause that person . . . to suffer serious emotional distress."

>> 4. Supreme court sides with weird dude

Partially. They decided that to convict, you need to show that there was intent:

"The first dispute here is about whether the First Amendment nonetheless demands that the State in a true threats case prove that the defendant was aware in some way of the threatening nature of his communications. Colorado argues that there is no such requirement. Counterman contends that there is one, based mainly on the likelihood that the absence of such a mens rea requirement will chill protected, non-threatening speech. Counterman’s view, we decide today, is the more consistent with our precedent."

But also:

"The second issue here concerns what precise mens rea standard suffices for the First Amendment purpose at issue. Again guided by our precedent, we hold that a recklessness standard is enough. Given that a subjective standard here shields speech not independently entitled to protection - and indeed posing real dangers - we do not require that the State prove the defendant had any more specific intent to threaten the victim."

So in my non-lawerly understanding, you have to show intent, but a pretty low standard of intent, recklessness: "A person acts recklessly, in the most common formulation, when he "consciously disregard[s] a substantial [and unjustifiable] risk that the conduct will cause harm to another.""

So they can retry the case, just need to show reckless intent this time. Don't need to show intent to threaten let alone intent to carry out threats.