Two possibilities that I can think of. One, the New Madrid Seismic Zone is overdue for a rupture. When it goes, there won't be a bridge left on the Mississippi, and the government has been planning for it for well over a decade. Two, with the moon blocking most of the light from the Sun, Nibiru may become visible to millions of people, who are going to want to know why this extinction level visitor was kept secret from them. Both would require martial law to be enacted.