Because personal data about US citizens is up for sale to more or less whoever wants it, and the US government doesn’t seem to have a problem with this otherwise.

Which makes it seem far more plausible that the real national security capability that is being defended is that of the US gov to influence narratives on social media. And while even that might be constitutional, it’s a lot less compelling.

Laws don't have to solve all of the potential problems that may exist in order to be valid (this is one of the things they talk about in the decision).

However, there is another law that made sale of data to foreign adversaries illegal, passed in April 2024: https://www.congress.gov/bill/118th-congress/house-bill/7520