For all I know BB and his crazy brother dispersed the mist as a result of Thanos attack in infinity intentionally but few know that most believe it was some kind of accident.
In Uncanny Inhumans Medusa in a conversation with BB made to understand that more Inhumans were needed for some kind of war or conflict in the future and they would need humans and mutants help if they want to survive this.
So it is not strange that Cyclops believe the Inhumans are responsible as he is unaware of the facts and from their point of view and probably any normal person or leader of a people or country would believe they were being attacked or were about to enter in a war.What is funny since wars began for much less considering the situation Scott has every reason to believe that a war is about to begin.
Remember that BB despite losing his throne he still has much influence with various Inhumans working for him and he and his club has made connections with all kinds of people including villains and companies serving as some sort of neutral meeting place.