They weren't buying insurance. There's no insurance payout for the companies. They got a small amount of money in hand, and lost the chance to reclaim any of the tariff refund. That isn't insurance.

Also, the SCOTUS is not a criminal court, it is a constitutional court. If a case is heard there, both sides have not agreed on "obvious illegality". That is unsuprising since in general one side (in this case, the administrative branch of the US Government) is being accused of illegal behavior - when it comes to constitutional rather than criminal questions, most parties do not just accept their guilt, but push as far as they can towards exoneration.

Frequently, however to everybody else, the case concerns obvious illegality.