This ruling makes sense to me:

Assuming, without deciding, that this [anti-corruption] interest is compelling, the formation deadline is unconstitutional because it is not narrowly tailored. The formation deadline indiscriminately prohibits (or significantly burdens) speech by individuals or groups who did not form a campaign committee by the 30-day deadline. This would be less burdensome if all individuals and groups knew well in advance that they would eventually want to speak. But as the Supreme Court has recognized, this is not the case…