https://www.supremecourt.gov/opinions/23pdf/23-411_3dq3.pdf
it sounds as if this was just a terribly-made case. The plaintiffs never even tried to assert an actual problem. They just made up potential problems. The decision is pretty harsh: "But they do not point to any specific instance of content moderation that caused them identifiable harm."
"Lack of standing" is a pretty standard tactic for when the Supreme Court doesn't want to make a decision on the merits. That way they leave room for a better case to be made some day, by somebody else.
It's actually concerning that someone would link to this here.