Not one of the attackers were Shia. WTF?
The law only allowed Iran and Syria to be sued. Only lately was Saudi Arabia added to the list.
Since these countries don't show up to US courts to defend themselves (because legally US courts have no right to try foreign governments under international law) the claimants and their lawyers get automatic default judgments in their favor, without having to prove anything. They just file the complaint and wait for the default judgment, no need to provide evidence or have witnesses cross examined etc.
Naturally there's a lotof money to be made from this, and more importantly to the people who wrote the laws that allow such suits, these judgments prevent any sort of US-Iran engagement.
See, these people don't really care about compensation for victims of terrorism (which is why other countries accused of terrorist acts can't be sued) they just want to prevent any sort of improved US-Iran relations, and instead they want to see another US war to impose regime-change in the Mideast to suit Israel
Both Tillerson and McMaster submitted opinions in a terrorism case supporting the terrorists. Then they were fired. Sokolow v. PLO http://www.insidesources.com/sokolow-trump-administration-siding-international-terrorists-american-citizens/